xref: /net/unix/af_unix.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * NET4:	Implementation of BSD Unix domain sockets.
 *
 * Authors:	Alan Cox, <alan@lxorguk.ukuu.org.uk>
 *
 * Fixes:
 *		Linus Torvalds	:	Assorted bug cures.
 *		Niibe Yutaka	:	async I/O support.
 *		Carsten Paeth	:	PF_UNIX check, address fixes.
 *		Alan Cox	:	Limit size of allocated blocks.
 *		Alan Cox	:	Fixed the stupid socketpair bug.
 *		Alan Cox	:	BSD compatibility fine tuning.
 *		Alan Cox	:	Fixed a bug in connect when interrupted.
 *		Alan Cox	:	Sorted out a proper draft version of
 *					file descriptor passing hacked up from
 *					Mike Shaver's work.
 *		Marty Leisner	:	Fixes to fd passing
 *		Nick Nevin	:	recvmsg bugfix.
 *		Alan Cox	:	Started proper garbage collector
 *		Heiko EiBfeldt	:	Missing verify_area check
 *		Alan Cox	:	Started POSIXisms
 *		Andreas Schwab	:	Replace inode by dentry for proper
 *					reference counting
 *		Kirk Petersen	:	Made this a module
 *	    Christoph Rohland	:	Elegant non-blocking accept/connect algorithm.
 *					Lots of bug fixes.
 *	     Alexey Kuznetosv	:	Repaired (I hope) bugs introduces
 *					by above two patches.
 *	     Andrea Arcangeli	:	If possible we block in connect(2)
 *					if the max backlog of the listen socket
 *					is been reached. This won't break
 *					old apps and it will avoid huge amount
 *					of socks hashed (this for unix_gc()
 *					performances reasons).
 *					Security fix that limits the max
 *					number of socks to 2*max_files and
 *					the number of skb queueable in the
 *					dgram receiver.
 *		Artur Skawina   :	Hash function optimizations
 *	     Alexey Kuznetsov   :	Full scale SMP. Lot of bugs are introduced 8)
 *	      Malcolm Beattie   :	Set peercred for socketpair
 *	     Michal Ostrowski   :       Module initialization cleanup.
 *	     Arnaldo C. Melo	:	Remove MOD_{INC,DEC}_USE_COUNT,
 *	     				the core infrastructure is doing that
 *	     				for all net proto families now (2.5.69+)
 *
 * Known differences from reference BSD that was tested:
 *
 *	[TO FIX]
 *	ECONNREFUSED is not returned from one end of a connected() socket to the
 *		other the moment one end closes.
 *	fstat() doesn't return st_dev=0, and give the blksize as high water mark
 *		and a fake inode identifier (nor the BSD first socket fstat twice bug).
 *	[NOT TO FIX]
 *	accept() returns a path name even if the connecting socket has closed
 *		in the meantime (BSD loses the path and gives up).
 *	accept() returns 0 length path for an unbound connector. BSD returns 16
 *		and a null first byte in the path (but not for gethost/peername - BSD bug ??)
 *	socketpair(...SOCK_RAW..) doesn't panic the kernel.
 *	BSD af_unix apparently has connect forgetting to block properly.
 *		(need to check this with the POSIX spec in detail)
 *
 * Differences from 2.0.0-11-... (ANK)
 *	Bug fixes and improvements.
 *		- client shutdown killed server socket.
 *		- removed all useless cli/sti pairs.
 *
 *	Semantic changes/extensions.
 *		- generic control message passing.
 *		- SCM_CREDENTIALS control message.
 *		- "Abstract" (not FS based) socket bindings.
 *		  Abstract names are sequences of bytes (not zero terminated)
 *		  started by 0, so that this name space does not intersect
 *		  with BSD names.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched/signal.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/fcntl.h>
#include <linux/filter.h>
#include <linux/termios.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/in.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/af_unix.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <net/scm.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/rtnetlink.h>
#include <linux/mount.h>
#include <net/checksum.h>
#include <linux/security.h>
#include <linux/splice.h>
#include <linux/freezer.h>
#include <linux/file.h>
#include <linux/btf_ids.h>

#include "scm.h"

static atomic_long_t unix_nr_socks;
static struct hlist_head bsd_socket_buckets[UNIX_HASH_SIZE / 2];
static spinlock_t bsd_socket_locks[UNIX_HASH_SIZE / 2];

/* SMP locking strategy:
 *    hash table is protected with spinlock.
 *    each socket state is protected by separate spinlock.
 */

static unsigned int unix_unbound_hash(struct sock *sk)
{
	unsigned long hash = (unsigned long)sk;

	hash ^= hash >> 16;
	hash ^= hash >> 8;
	hash ^= sk->sk_type;

	return hash & UNIX_HASH_MOD;
}

static unsigned int unix_bsd_hash(struct inode *i)
{
	return i->i_ino & UNIX_HASH_MOD;
}

static unsigned int unix_abstract_hash(struct sockaddr_un *sunaddr,
				       int addr_len, int type)
{
	__wsum csum = csum_partial(sunaddr, addr_len, 0);
	unsigned int hash;

	hash = (__force unsigned int)csum_fold(csum);
	hash ^= hash >> 8;
	hash ^= type;

	return UNIX_HASH_MOD + 1 + (hash & UNIX_HASH_MOD);
}

static void unix_table_double_lock(struct net *net,
				   unsigned int hash1, unsigned int hash2)
{
	if (hash1 == hash2) {
		spin_lock(&net->unx.table.locks[hash1]);
		return;
	}

	if (hash1 > hash2)
		swap(hash1, hash2);

	spin_lock(&net->unx.table.locks[hash1]);
	spin_lock_nested(&net->unx.table.locks[hash2], SINGLE_DEPTH_NESTING);
}

static void unix_table_double_unlock(struct net *net,
				     unsigned int hash1, unsigned int hash2)
{
	if (hash1 == hash2) {
		spin_unlock(&net->unx.table.locks[hash1]);
		return;
	}

	spin_unlock(&net->unx.table.locks[hash1]);
	spin_unlock(&net->unx.table.locks[hash2]);
}

#ifdef CONFIG_SECURITY_NETWORK
static void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
{
	UNIXCB(skb).secid = scm->secid;
}

static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
{
	scm->secid = UNIXCB(skb).secid;
}

static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
{
	return (scm->secid == UNIXCB(skb).secid);
}
#else
static inline void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
{ }

static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
{ }

static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
{
	return true;
}
#endif /* CONFIG_SECURITY_NETWORK */

static inline int unix_our_peer(struct sock *sk, struct sock *osk)
{
	return unix_peer(osk) == sk;
}

static inline int unix_may_send(struct sock *sk, struct sock *osk)
{
	return unix_peer(osk) == NULL || unix_our_peer(sk, osk);
}

static inline int unix_recvq_full_lockless(const struct sock *sk)
{
	return skb_queue_len_lockless(&sk->sk_receive_queue) > sk->sk_max_ack_backlog;
}

struct sock *unix_peer_get(struct sock *s)
{
	struct sock *peer;

	unix_state_lock(s);
	peer = unix_peer(s);
	if (peer)
		sock_hold(peer);
	unix_state_unlock(s);
	return peer;
}
EXPORT_SYMBOL_GPL(unix_peer_get);

static struct unix_address *unix_create_addr(struct sockaddr_un *sunaddr,
					     int addr_len)
{
	struct unix_address *addr;

	addr = kmalloc(sizeof(*addr) + addr_len, GFP_KERNEL);
	if (!addr)
		return NULL;

	refcount_set(&addr->refcnt, 1);
	addr->len = addr_len;
	memcpy(addr->name, sunaddr, addr_len);

	return addr;
}

static inline void unix_release_addr(struct unix_address *addr)
{
	if (refcount_dec_and_test(&addr->refcnt))
		kfree(addr);
}

/*
 *	Check unix socket name:
 *		- should be not zero length.
 *	        - if started by not zero, should be NULL terminated (FS object)
 *		- if started by zero, it is abstract name.
 */

static int unix_validate_addr(struct sockaddr_un *sunaddr, int addr_len)
{
	if (addr_len <= offsetof(struct sockaddr_un, sun_path) ||
	    addr_len > sizeof(*sunaddr))
		return -EINVAL;

	if (sunaddr->sun_family != AF_UNIX)
		return -EINVAL;

	return 0;
}

static int unix_mkname_bsd(struct sockaddr_un *sunaddr, int addr_len)
{
	struct sockaddr_storage *addr = (struct sockaddr_storage *)sunaddr;
	short offset = offsetof(struct sockaddr_storage, __data);

	BUILD_BUG_ON(offset != offsetof(struct sockaddr_un, sun_path));

	/* This may look like an off by one error but it is a bit more
	 * subtle.  108 is the longest valid AF_UNIX path for a binding.
	 * sun_path[108] doesn't as such exist.  However in kernel space
	 * we are guaranteed that it is a valid memory location in our
	 * kernel address buffer because syscall functions always pass
	 * a pointer of struct sockaddr_storage which has a bigger buffer
	 * than 108.  Also, we must terminate sun_path for strlen() in
	 * getname_kernel().
	 */
	addr->__data[addr_len - offset] = 0;

	/* Don't pass sunaddr->sun_path to strlen().  Otherwise, 108 will
	 * cause panic if CONFIG_FORTIFY_SOURCE=y.  Let __fortify_strlen()
	 * know the actual buffer.
	 */
	return strlen(addr->__data) + offset + 1;
}

static void __unix_remove_socket(struct sock *sk)
{
	sk_del_node_init(sk);
}

static void __unix_insert_socket(struct net *net, struct sock *sk)
{
	DEBUG_NET_WARN_ON_ONCE(!sk_unhashed(sk));
	sk_add_node(sk, &net->unx.table.buckets[sk->sk_hash]);
}

static void __unix_set_addr_hash(struct net *net, struct sock *sk,
				 struct unix_address *addr, unsigned int hash)
{
	__unix_remove_socket(sk);
	smp_store_release(&unix_sk(sk)->addr, addr);

	sk->sk_hash = hash;
	__unix_insert_socket(net, sk);
}

static void unix_remove_socket(struct net *net, struct sock *sk)
{
	spin_lock(&net->unx.table.locks[sk->sk_hash]);
	__unix_remove_socket(sk);
	spin_unlock(&net->unx.table.locks[sk->sk_hash]);
}

static void unix_insert_unbound_socket(struct net *net, struct sock *sk)
{
	spin_lock(&net->unx.table.locks[sk->sk_hash]);
	__unix_insert_socket(net, sk);
	spin_unlock(&net->unx.table.locks[sk->sk_hash]);
}

static void unix_insert_bsd_socket(struct sock *sk)
{
	spin_lock(&bsd_socket_locks[sk->sk_hash]);
	sk_add_bind_node(sk, &bsd_socket_buckets[sk->sk_hash]);
	spin_unlock(&bsd_socket_locks[sk->sk_hash]);
}

static void unix_remove_bsd_socket(struct sock *sk)
{
	if (!hlist_unhashed(&sk->sk_bind_node)) {
		spin_lock(&bsd_socket_locks[sk->sk_hash]);
		__sk_del_bind_node(sk);
		spin_unlock(&bsd_socket_locks[sk->sk_hash]);

		sk_node_init(&sk->sk_bind_node);
	}
}

static struct sock *__unix_find_socket_byname(struct net *net,
					      struct sockaddr_un *sunname,
					      int len, unsigned int hash)
{
	struct sock *s;

	sk_for_each(s, &net->unx.table.buckets[hash]) {
		struct unix_sock *u = unix_sk(s);

		if (u->addr->len == len &&
		    !memcmp(u->addr->name, sunname, len))
			return s;
	}
	return NULL;
}

static inline struct sock *unix_find_socket_byname(struct net *net,
						   struct sockaddr_un *sunname,
						   int len, unsigned int hash)
{
	struct sock *s;

	spin_lock(&net->unx.table.locks[hash]);
	s = __unix_find_socket_byname(net, sunname, len, hash);
	if (s)
		sock_hold(s);
	spin_unlock(&net->unx.table.locks[hash]);
	return s;
}

static struct sock *unix_find_socket_byinode(struct inode *i)
{
	unsigned int hash = unix_bsd_hash(i);
	struct sock *s;

	spin_lock(&bsd_socket_locks[hash]);
	sk_for_each_bound(s, &bsd_socket_buckets[hash]) {
		struct dentry *dentry = unix_sk(s)->path.dentry;

		if (dentry && d_backing_inode(dentry) == i) {
			sock_hold(s);
			spin_unlock(&bsd_socket_locks[hash]);
			return s;
		}
	}
	spin_unlock(&bsd_socket_locks[hash]);
	return NULL;
}

/* Support code for asymmetrically connected dgram sockets
 *
 * If a datagram socket is connected to a socket not itself connected
 * to the first socket (eg, /dev/log), clients may only enqueue more
 * messages if the present receive queue of the server socket is not
 * "too large". This means there's a second writeability condition
 * poll and sendmsg need to test. The dgram recv code will do a wake
 * up on the peer_wait wait queue of a socket upon reception of a
 * datagram which needs to be propagated to sleeping would-be writers
 * since these might not have sent anything so far. This can't be
 * accomplished via poll_wait because the lifetime of the server
 * socket might be less than that of its clients if these break their
 * association with it or if the server socket is closed while clients
 * are still connected to it and there's no way to inform "a polling
 * implementation" that it should let go of a certain wait queue
 *
 * In order to propagate a wake up, a wait_queue_entry_t of the client
 * socket is enqueued on the peer_wait queue of the server socket
 * whose wake function does a wake_up on the ordinary client socket
 * wait queue. This connection is established whenever a write (or
 * poll for write) hit the flow control condition and broken when the
 * association to the server socket is dissolved or after a wake up
 * was relayed.
 */

static int unix_dgram_peer_wake_relay(wait_queue_entry_t *q, unsigned mode, int flags,
				      void *key)
{
	struct unix_sock *u;
	wait_queue_head_t *u_sleep;

	u = container_of(q, struct unix_sock, peer_wake);

	__remove_wait_queue(&unix_sk(u->peer_wake.private)->peer_wait,
			    q);
	u->peer_wake.private = NULL;

	/* relaying can only happen while the wq still exists */
	u_sleep = sk_sleep(&u->sk);
	if (u_sleep)
		wake_up_interruptible_poll(u_sleep, key_to_poll(key));

	return 0;
}

static int unix_dgram_peer_wake_connect(struct sock *sk, struct sock *other)
{
	struct unix_sock *u, *u_other;
	int rc;

	u = unix_sk(sk);
	u_other = unix_sk(other);
	rc = 0;
	spin_lock(&u_other->peer_wait.lock);

	if (!u->peer_wake.private) {
		u->peer_wake.private = other;
		__add_wait_queue(&u_other->peer_wait, &u->peer_wake);

		rc = 1;
	}

	spin_unlock(&u_other->peer_wait.lock);
	return rc;
}

static void unix_dgram_peer_wake_disconnect(struct sock *sk,
					    struct sock *other)
{
	struct unix_sock *u, *u_other;

	u = unix_sk(sk);
	u_other = unix_sk(other);
	spin_lock(&u_other->peer_wait.lock);

	if (u->peer_wake.private == other) {
		__remove_wait_queue(&u_other->peer_wait, &u->peer_wake);
		u->peer_wake.private = NULL;
	}

	spin_unlock(&u_other->peer_wait.lock);
}

static void unix_dgram_peer_wake_disconnect_wakeup(struct sock *sk,
						   struct sock *other)
{
	unix_dgram_peer_wake_disconnect(sk, other);
	wake_up_interruptible_poll(sk_sleep(sk),
				   EPOLLOUT |
				   EPOLLWRNORM |
				   EPOLLWRBAND);
}

/* preconditions:
 *	- unix_peer(sk) == other
 *	- association is stable
 */
static int unix_dgram_peer_wake_me(struct sock *sk, struct sock *other)
{
	int connected;

	connected = unix_dgram_peer_wake_connect(sk, other);

	/* If other is SOCK_DEAD, we want to make sure we signal
	 * POLLOUT, such that a subsequent write() can get a
	 * -ECONNREFUSED. Otherwise, if we haven't queued any skbs
	 * to other and its full, we will hang waiting for POLLOUT.
	 */
	if (unix_recvq_full_lockless(other) && !sock_flag(other, SOCK_DEAD))
		return 1;

	if (connected)
		unix_dgram_peer_wake_disconnect(sk, other);

	return 0;
}

static int unix_writable(const struct sock *sk, unsigned char state)
{
	return state != TCP_LISTEN &&
		(refcount_read(&sk->sk_wmem_alloc) << 2) <= READ_ONCE(sk->sk_sndbuf);
}

static void unix_write_space(struct sock *sk)
{
	struct socket_wq *wq;

	rcu_read_lock();
	if (unix_writable(sk, READ_ONCE(sk->sk_state))) {
		wq = rcu_dereference(sk->sk_wq);
		if (skwq_has_sleeper(wq))
			wake_up_interruptible_sync_poll(&wq->wait,
				EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND);
		sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT);
	}
	rcu_read_unlock();
}

/* When dgram socket disconnects (or changes its peer), we clear its receive
 * queue of packets arrived from previous peer. First, it allows to do
 * flow control based only on wmem_alloc; second, sk connected to peer
 * may receive messages only from that peer. */
static void unix_dgram_disconnected(struct sock *sk, struct sock *other)
{
	if (!skb_queue_empty(&sk->sk_receive_queue)) {
		skb_queue_purge(&sk->sk_receive_queue);
		wake_up_interruptible_all(&unix_sk(sk)->peer_wait);

		/* If one link of bidirectional dgram pipe is disconnected,
		 * we signal error. Messages are lost. Do not make this,
		 * when peer was not connected to us.
		 */
		if (!sock_flag(other, SOCK_DEAD) && unix_peer(other) == sk) {
			WRITE_ONCE(other->sk_err, ECONNRESET);
			sk_error_report(other);
		}
	}
}

static void unix_sock_destructor(struct sock *sk)
{
	struct unix_sock *u = unix_sk(sk);

	skb_queue_purge(&sk->sk_receive_queue);

	DEBUG_NET_WARN_ON_ONCE(refcount_read(&sk->sk_wmem_alloc));
	DEBUG_NET_WARN_ON_ONCE(!sk_unhashed(sk));
	DEBUG_NET_WARN_ON_ONCE(sk->sk_socket);
	if (!sock_flag(sk, SOCK_DEAD)) {
		pr_info("Attempt to release alive unix socket: %p\n", sk);
		return;
	}

	if (u->addr)
		unix_release_addr(u->addr);

	atomic_long_dec(&unix_nr_socks);
	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
#ifdef UNIX_REFCNT_DEBUG
	pr_debug("UNIX %p is destroyed, %ld are still alive.\n", sk,
		atomic_long_read(&unix_nr_socks));
#endif
}

static void unix_release_sock(struct sock *sk, int embrion)
{
	struct unix_sock *u = unix_sk(sk);
	struct sock *skpair;
	struct sk_buff *skb;
	struct path path;
	int state;

	unix_remove_socket(sock_net(sk), sk);
	unix_remove_bsd_socket(sk);

	/* Clear state */
	unix_state_lock(sk);
	sock_orphan(sk);
	WRITE_ONCE(sk->sk_shutdown, SHUTDOWN_MASK);
	path	     = u->path;
	u->path.dentry = NULL;
	u->path.mnt = NULL;
	state = sk->sk_state;
	WRITE_ONCE(sk->sk_state, TCP_CLOSE);

	skpair = unix_peer(sk);
	unix_peer(sk) = NULL;

	unix_state_unlock(sk);

#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
	if (u->oob_skb) {
		kfree_skb(u->oob_skb);
		u->oob_skb = NULL;
	}
#endif

	wake_up_interruptible_all(&u->peer_wait);

	if (skpair != NULL) {
		if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) {
			unix_state_lock(skpair);
			/* No more writes */
			WRITE_ONCE(skpair->sk_shutdown, SHUTDOWN_MASK);
			if (!skb_queue_empty_lockless(&sk->sk_receive_queue) || embrion)
				WRITE_ONCE(skpair->sk_err, ECONNRESET);
			unix_state_unlock(skpair);
			skpair->sk_state_change(skpair);
			sk_wake_async(skpair, SOCK_WAKE_WAITD, POLL_HUP);
		}

		unix_dgram_peer_wake_disconnect(sk, skpair);
		sock_put(skpair); /* It may now die */
	}

	/* Try to flush out this socket. Throw out buffers at least */

	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
		if (state == TCP_LISTEN)
			unix_release_sock(skb->sk, 1);
		/* passed fds are erased in the kfree_skb hook	      */
		UNIXCB(skb).consumed = skb->len;
		kfree_skb(skb);
	}

	if (path.dentry)
		path_put(&path);

	sock_put(sk);

	/* ---- Socket is dead now and most probably destroyed ---- */

	/*
	 * Fixme: BSD difference: In BSD all sockets connected to us get
	 *	  ECONNRESET and we die on the spot. In Linux we behave
	 *	  like files and pipes do and wait for the last
	 *	  dereference.
	 *
	 * Can't we simply set sock->err?
	 *
	 *	  What the above comment does talk about? --ANK(980817)
	 */

	if (READ_ONCE(unix_tot_inflight))
		unix_gc();		/* Garbage collect fds */
}

static void init_peercred(struct sock *sk)
{
	const struct cred *old_cred;
	struct pid *old_pid;

	spin_lock(&sk->sk_peer_lock);
	old_pid = sk->sk_peer_pid;
	old_cred = sk->sk_peer_cred;
	sk->sk_peer_pid  = get_pid(task_tgid(current));
	sk->sk_peer_cred = get_current_cred();
	spin_unlock(&sk->sk_peer_lock);

	put_pid(old_pid);
	put_cred(old_cred);
}

static void copy_peercred(struct sock *sk, struct sock *peersk)
{
	const struct cred *old_cred;
	struct pid *old_pid;

	if (sk < peersk) {
		spin_lock(&sk->sk_peer_lock);
		spin_lock_nested(&peersk->sk_peer_lock, SINGLE_DEPTH_NESTING);
	} else {
		spin_lock(&peersk->sk_peer_lock);
		spin_lock_nested(&sk->sk_peer_lock, SINGLE_DEPTH_NESTING);
	}
	old_pid = sk->sk_peer_pid;
	old_cred = sk->sk_peer_cred;
	sk->sk_peer_pid  = get_pid(peersk->sk_peer_pid);
	sk->sk_peer_cred = get_cred(peersk->sk_peer_cred);

	spin_unlock(&sk->sk_peer_lock);
	spin_unlock(&peersk->sk_peer_lock);

	put_pid(old_pid);
	put_cred(old_cred);
}

static int unix_listen(struct socket *sock, int backlog)
{
	int err;
	struct sock *sk = sock->sk;
	struct unix_sock *u = unix_sk(sk);

	err = -EOPNOTSUPP;
	if (sock->type != SOCK_STREAM && sock->type != SOCK_SEQPACKET)
		goto out;	/* Only stream/seqpacket sockets accept */
	err = -EINVAL;
	if (!READ_ONCE(u->addr))
		goto out;	/* No listens on an unbound socket */
	unix_state_lock(sk);
	if (sk->sk_state != TCP_CLOSE && sk->sk_state != TCP_LISTEN)
		goto out_unlock;
	if (backlog > sk->sk_max_ack_backlog)
		wake_up_interruptible_all(&u->peer_wait);
	sk->sk_max_ack_backlog	= backlog;
	WRITE_ONCE(sk->sk_state, TCP_LISTEN);

	/* set credentials so connect can copy them */
	init_peercred(sk);
	err = 0;

out_unlock:
	unix_state_unlock(sk);
out:
	return err;
}

static int unix_release(struct socket *);
static int unix_bind(struct socket *, struct sockaddr *, int);
static int unix_stream_connect(struct socket *, struct sockaddr *,
			       int addr_len, int flags);
static int unix_socketpair(struct socket *, struct socket *);
static int unix_accept(struct socket *, struct socket *, int, bool);
static int unix_getname(struct socket *, struct sockaddr *, int);
static __poll_t unix_poll(struct file *, struct socket *, poll_table *);
static __poll_t unix_dgram_poll(struct file *, struct socket *,
				    poll_table *);
static int unix_ioctl(struct socket *, unsigned int, unsigned long);
#ifdef CONFIG_COMPAT
static int unix_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
#endif
static int unix_shutdown(struct socket *, int);
static int unix_stream_sendmsg(struct socket *, struct msghdr *, size_t);
static int unix_stream_recvmsg(struct socket *, struct msghdr *, size_t, int);
static ssize_t unix_stream_splice_read(struct socket *,  loff_t *ppos,
				       struct pipe_inode_info *, size_t size,
				       unsigned int flags);
static int unix_dgram_sendmsg(struct socket *, struct msghdr *, size_t);
static int unix_dgram_recvmsg(struct socket *, struct msghdr *, size_t, int);
static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor);
static int unix_dgram_connect(struct socket *, struct sockaddr *,
			      int, int);
static int unix_seqpacket_sendmsg(struct socket *, struct msghdr *, size_t);
static int unix_seqpacket_recvmsg(struct socket *, struct msghdr *, size_t,
				  int);

static int unix_set_peek_off(struct sock *sk, int val)
{
	struct unix_sock *u = unix_sk(sk);

	if (mutex_lock_interruptible(&u->iolock))
		return -EINTR;

	WRITE_ONCE(sk->sk_peek_off, val);
	mutex_unlock(&u->iolock);

	return 0;
}

#ifdef CONFIG_PROC_FS
static int unix_count_nr_fds(struct sock *sk)
{
	struct sk_buff *skb;
	struct unix_sock *u;
	int nr_fds = 0;

	spin_lock(&sk->sk_receive_queue.lock);
	skb = skb_peek(&sk->sk_receive_queue);
	while (skb) {
		u = unix_sk(skb->sk);
		nr_fds += atomic_read(&u->scm_stat.nr_fds);
		skb = skb_peek_next(skb, &sk->sk_receive_queue);
	}
	spin_unlock(&sk->sk_receive_queue.lock);

	return nr_fds;
}

static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
{
	struct sock *sk = sock->sk;
	unsigned char s_state;
	struct unix_sock *u;
	int nr_fds = 0;

	if (sk) {
		s_state = READ_ONCE(sk->sk_state);
		u = unix_sk(sk);

		/* SOCK_STREAM and SOCK_SEQPACKET sockets never change their
		 * sk_state after switching to TCP_ESTABLISHED or TCP_LISTEN.
		 * SOCK_DGRAM is ordinary. So, no lock is needed.
		 */
		if (sock->type == SOCK_DGRAM || s_state == TCP_ESTABLISHED)
			nr_fds = atomic_read(&u->scm_stat.nr_fds);
		else if (s_state == TCP_LISTEN)
			nr_fds = unix_count_nr_fds(sk);

		seq_printf(m, "scm_fds: %u\n", nr_fds);
	}
}
#else
#define unix_show_fdinfo NULL
#endif

static const struct proto_ops unix_stream_ops = {
	.family =	PF_UNIX,
	.owner =	THIS_MODULE,
	.release =	unix_release,
	.bind =		unix_bind,
	.connect =	unix_stream_connect,
	.socketpair =	unix_socketpair,
	.accept =	unix_accept,
	.getname =	unix_getname,
	.poll =		unix_poll,
	.ioctl =	unix_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl =	unix_compat_ioctl,
#endif
	.listen =	unix_listen,
	.shutdown =	unix_shutdown,
	.sendmsg =	unix_stream_sendmsg,
	.recvmsg =	unix_stream_recvmsg,
	.read_skb =	unix_stream_read_skb,
	.mmap =		sock_no_mmap,
	.splice_read =	unix_stream_splice_read,
	.set_peek_off =	unix_set_peek_off,
	.show_fdinfo =	unix_show_fdinfo,
};

static const struct proto_ops unix_dgram_ops = {
	.family =	PF_UNIX,
	.owner =	THIS_MODULE,
	.release =	unix_release,
	.bind =		unix_bind,
	.connect =	unix_dgram_connect,
	.socketpair =	unix_socketpair,
	.accept =	sock_no_accept,
	.getname =	unix_getname,
	.poll =		unix_dgram_poll,
	.ioctl =	unix_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl =	unix_compat_ioctl,
#endif
	.listen =	sock_no_listen,
	.shutdown =	unix_shutdown,
	.sendmsg =	unix_dgram_sendmsg,
	.read_skb =	unix_read_skb,
	.recvmsg =	unix_dgram_recvmsg,
	.mmap =		sock_no_mmap,
	.set_peek_off =	unix_set_peek_off,
	.show_fdinfo =	unix_show_fdinfo,
};

static const struct proto_ops unix_seqpacket_ops = {
	.family =	PF_UNIX,
	.owner =	THIS_MODULE,
	.release =	unix_release,
	.bind =		unix_bind,
	.connect =	unix_stream_connect,
	.socketpair =	unix_socketpair,
	.accept =	unix_accept,
	.getname =	unix_getname,
	.poll =		unix_dgram_poll,
	.ioctl =	unix_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl =	unix_compat_ioctl,
#endif
	.listen =	unix_listen,
	.shutdown =	unix_shutdown,
	.sendmsg =	unix_seqpacket_sendmsg,
	.recvmsg =	unix_seqpacket_recvmsg,
	.mmap =		sock_no_mmap,
	.set_peek_off =	unix_set_peek_off,
	.show_fdinfo =	unix_show_fdinfo,
};

static void unix_close(struct sock *sk, long timeout)
{
	/* Nothing to do here, unix socket does not need a ->close().
	 * This is merely for sockmap.
	 */
}

static void unix_unhash(struct sock *sk)
{
	/* Nothing to do here, unix socket does not need a ->unhash().
	 * This is merely for sockmap.
	 */
}

static bool unix_bpf_bypass_getsockopt(int level, int optname)
{
	if (level == SOL_SOCKET) {
		switch (optname) {
		case SO_PEERPIDFD:
			return true;
		default:
			return false;
		}
	}

	return false;
}

struct proto unix_dgram_proto = {
	.name			= "UNIX",
	.owner			= THIS_MODULE,
	.obj_size		= sizeof(struct unix_sock),
	.close			= unix_close,
	.bpf_bypass_getsockopt	= unix_bpf_bypass_getsockopt,
#ifdef CONFIG_BPF_SYSCALL
	.psock_update_sk_prot	= unix_dgram_bpf_update_proto,
#endif
};

struct proto unix_stream_proto = {
	.name			= "UNIX-STREAM",
	.owner			= THIS_MODULE,
	.obj_size		= sizeof(struct unix_sock),
	.close			= unix_close,
	.unhash			= unix_unhash,
	.bpf_bypass_getsockopt	= unix_bpf_bypass_getsockopt,
#ifdef CONFIG_BPF_SYSCALL
	.psock_update_sk_prot	= unix_stream_bpf_update_proto,
#endif
};

static struct sock *unix_create1(struct net *net, struct socket *sock, int kern, int type)
{
	struct unix_sock *u;
	struct sock *sk;
	int err;

	atomic_long_inc(&unix_nr_socks);
	if (atomic_long_read(&unix_nr_socks) > 2 * get_max_files()) {
		err = -ENFILE;
		goto err;
	}

	if (type == SOCK_STREAM)
		sk = sk_alloc(net, PF_UNIX, GFP_KERNEL, &unix_stream_proto, kern);
	else /*dgram and  seqpacket */
		sk = sk_alloc(net, PF_UNIX, GFP_KERNEL, &unix_dgram_proto, kern);

	if (!sk) {
		err = -ENOMEM;
		goto err;
	}

	sock_init_data(sock, sk);

	sk->sk_hash		= unix_unbound_hash(sk);
	sk->sk_allocation	= GFP_KERNEL_ACCOUNT;
	sk->sk_write_space	= unix_write_space;
	sk->sk_max_ack_backlog	= READ_ONCE(net->unx.sysctl_max_dgram_qlen);
	sk->sk_destruct		= unix_sock_destructor;
	u = unix_sk(sk);
	u->inflight = 0;
	u->path.dentry = NULL;
	u->path.mnt = NULL;
	spin_lock_init(&u->lock);
	INIT_LIST_HEAD(&u->link);
	mutex_init(&u->iolock); /* single task reading lock */
	mutex_init(&u->bindlock); /* single task binding lock */
	init_waitqueue_head(&u->peer_wait);
	init_waitqueue_func_entry(&u->peer_wake, unix_dgram_peer_wake_relay);
	memset(&u->scm_stat, 0, sizeof(struct scm_stat));
	unix_insert_unbound_socket(net, sk);

	sock_prot_inuse_add(net, sk->sk_prot, 1);

	return sk;

err:
	atomic_long_dec(&unix_nr_socks);
	return ERR_PTR(err);
}

static int unix_create(struct net *net, struct socket *sock, int protocol,
		       int kern)
{
	struct sock *sk;

	if (protocol && protocol != PF_UNIX)
		return -EPROTONOSUPPORT;

	sock->state = SS_UNCONNECTED;

	switch (sock->type) {
	case SOCK_STREAM:
		sock->ops = &unix_stream_ops;
		break;
		/*
		 *	Believe it or not BSD has AF_UNIX, SOCK_RAW though
		 *	nothing uses it.
		 */
	case SOCK_RAW:
		sock->type = SOCK_DGRAM;
		fallthrough;
	case SOCK_DGRAM:
		sock->ops = &unix_dgram_ops;
		break;
	case SOCK_SEQPACKET:
		sock->ops = &unix_seqpacket_ops;
		break;
	default:
		return -ESOCKTNOSUPPORT;
	}

	sk = unix_create1(net, sock, kern, sock->type);
	if (IS_ERR(sk))
		return PTR_ERR(sk);

	return 0;
}

static int unix_release(struct socket *sock)
{
	struct sock *sk = sock->sk;

	if (!sk)
		return 0;

	sk->sk_prot->close(sk, 0);
	unix_release_sock(sk, 0);
	sock->sk = NULL;

	return 0;
}

static struct sock *unix_find_bsd(struct sockaddr_un *sunaddr, int addr_len,
				  int type)
{
	struct inode *inode;
	struct path path;
	struct sock *sk;
	int err;

	unix_mkname_bsd(sunaddr, addr_len);
	err = kern_path(sunaddr->sun_path, LOOKUP_FOLLOW, &path);
	if (err)
		goto fail;

	err = path_permission(&path, MAY_WRITE);
	if (err)
		goto path_put;

	err = -ECONNREFUSED;
	inode = d_backing_inode(path.dentry);
	if (!S_ISSOCK(inode->i_mode))
		goto path_put;

	sk = unix_find_socket_byinode(inode);
	if (!sk)
		goto path_put;

	err = -EPROTOTYPE;
	if (sk->sk_type == type)
		touch_atime(&path);
	else
		goto sock_put;

	path_put(&path);

	return sk;

sock_put:
	sock_put(sk);
path_put:
	path_put(&path);
fail:
	return ERR_PTR(err);
}

static struct sock *unix_find_abstract(struct net *net,
				       struct sockaddr_un *sunaddr,
				       int addr_len, int type)
{
	unsigned int hash = unix_abstract_hash(sunaddr, addr_len, type);
	struct dentry *dentry;
	struct sock *sk;

	sk = unix_find_socket_byname(net, sunaddr, addr_len, hash);
	if (!sk)
		return ERR_PTR(-ECONNREFUSED);

	dentry = unix_sk(sk)->path.dentry;
	if (dentry)
		touch_atime(&unix_sk(sk)->path);

	return sk;
}

static struct sock *unix_find_other(struct net *net,
				    struct sockaddr_un *sunaddr,
				    int addr_len, int type)
{
	struct sock *sk;

	if (sunaddr->sun_path[0])
		sk = unix_find_bsd(sunaddr, addr_len, type);
	else
		sk = unix_find_abstract(net, sunaddr, addr_len, type);

	return sk;
}

static int unix_autobind(struct sock *sk)
{
	struct unix_sock *u = unix_sk(sk);
	unsigned int new_hash, old_hash;
	struct net *net = sock_net(sk);
	struct unix_address *addr;
	u32 lastnum, ordernum;
	int err;

	err = mutex_lock_interruptible(&u->bindlock);
	if (err)
		return err;

	if (u->addr)
		goto out;

	err = -ENOMEM;
	addr = kzalloc(sizeof(*addr) +
		       offsetof(struct sockaddr_un, sun_path) + 16, GFP_KERNEL);
	if (!addr)
		goto out;

	addr->len = offsetof(struct sockaddr_un, sun_path) + 6;
	addr->name->sun_family = AF_UNIX;
	refcount_set(&addr->refcnt, 1);

	old_hash = sk->sk_hash;
	ordernum = get_random_u32();
	lastnum = ordernum & 0xFFFFF;
retry:
	ordernum = (ordernum + 1) & 0xFFFFF;
	sprintf(addr->name->sun_path + 1, "%05x", ordernum);

	new_hash = unix_abstract_hash(addr->name, addr->len, sk->sk_type);
	unix_table_double_lock(net, old_hash, new_hash);

	if (__unix_find_socket_byname(net, addr->name, addr->len, new_hash)) {
		unix_table_double_unlock(net, old_hash, new_hash);

		/* __unix_find_socket_byname() may take long time if many names
		 * are already in use.
		 */
		cond_resched();

		if (ordernum == lastnum) {
			/* Give up if all names seems to be in use. */
			err = -ENOSPC;
			unix_release_addr(addr);
			goto out;
		}

		goto retry;
	}

	__unix_set_addr_hash(net, sk, addr, new_hash);
	unix_table_double_unlock(net, old_hash, new_hash);
	err = 0;

out:	mutex_unlock(&u->bindlock);
	return err;
}

static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr,
			 int addr_len)
{
	umode_t mode = S_IFSOCK |
	       (SOCK_INODE(sk->sk_socket)->i_mode & ~current_umask());
	struct unix_sock *u = unix_sk(sk);
	unsigned int new_hash, old_hash;
	struct net *net = sock_net(sk);
	struct mnt_idmap *idmap;
	struct unix_address *addr;
	struct dentry *dentry;
	struct path parent;
	int err;

	addr_len = unix_mkname_bsd(sunaddr, addr_len);
	addr = unix_create_addr(sunaddr, addr_len);
	if (!addr)
		return -ENOMEM;

	/*
	 * Get the parent directory, calculate the hash for last
	 * component.
	 */
	dentry = kern_path_create(AT_FDCWD, addr->name->sun_path, &parent, 0);
	if (IS_ERR(dentry)) {
		err = PTR_ERR(dentry);
		goto out;
	}

	/*
	 * All right, let's create it.
	 */
	idmap = mnt_idmap(parent.mnt);
	err = security_path_mknod(&parent, dentry, mode, 0);
	if (!err)
		err = vfs_mknod(idmap, d_inode(parent.dentry), dentry, mode, 0);
	if (err)
		goto out_path;
	err = mutex_lock_interruptible(&u->bindlock);
	if (err)
		goto out_unlink;
	if (u->addr)
		goto out_unlock;

	old_hash = sk->sk_hash;
	new_hash = unix_bsd_hash(d_backing_inode(dentry));
	unix_table_double_lock(net, old_hash, new_hash);
	u->path.mnt = mntget(parent.mnt);
	u->path.dentry = dget(dentry);
	__unix_set_addr_hash(net, sk, addr, new_hash);
	unix_table_double_unlock(net, old_hash, new_hash);
	unix_insert_bsd_socket(sk);
	mutex_unlock(&u->bindlock);
	done_path_create(&parent, dentry);
	return 0;

out_unlock:
	mutex_unlock(&u->bindlock);
	err = -EINVAL;
out_unlink:
	/* failed after successful mknod?  unlink what we'd created... */
	vfs_unlink(idmap, d_inode(parent.dentry), dentry, NULL);
out_path:
	done_path_create(&parent, dentry);
out:
	unix_release_addr(addr);
	return err == -EEXIST ? -EADDRINUSE : err;
}

static int unix_bind_abstract(struct sock *sk, struct sockaddr_un *sunaddr,
			      int addr_len)
{
	struct unix_sock *u = unix_sk(sk);
	unsigned int new_hash, old_hash;
	struct net *net = sock_net(sk);
	struct unix_address *addr;
	int err;

	addr = unix_create_addr(sunaddr, addr_len);
	if (!addr)
		return -ENOMEM;

	err = mutex_lock_interruptible(&u->bindlock);
	if (err)
		goto out;

	if (u->addr) {
		err = -EINVAL;
		goto out_mutex;
	}

	old_hash = sk->sk_hash;
	new_hash = unix_abstract_hash(addr->name, addr->len, sk->sk_type);
	unix_table_double_lock(net, old_hash, new_hash);

	if (__unix_find_socket_byname(net, addr->name, addr->len, new_hash))
		goto out_spin;

	__unix_set_addr_hash(net, sk, addr, new_hash);
	unix_table_double_unlock(net, old_hash, new_hash);
	mutex_unlock(&u->bindlock);
	return 0;

out_spin:
	unix_table_double_unlock(net, old_hash, new_hash);
	err = -EADDRINUSE;
out_mutex:
	mutex_unlock(&u->bindlock);
out:
	unix_release_addr(addr);
	return err;
}

static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
	struct sockaddr_un *sunaddr = (struct sockaddr_un *)uaddr;
	struct sock *sk = sock->sk;
	int err;

	if (addr_len == offsetof(struct sockaddr_un, sun_path) &&
	    sunaddr->sun_family == AF_UNIX)
		return unix_autobind(sk);

	err = unix_validate_addr(sunaddr, addr_len);
	if (err)
		return err;

	if (sunaddr->sun_path[0])
		err = unix_bind_bsd(sk, sunaddr, addr_len);
	else
		err = unix_bind_abstract(sk, sunaddr, addr_len);

	return err;
}

static void unix_state_double_lock(struct sock *sk1, struct sock *sk2)
{
	if (unlikely(sk1 == sk2) || !sk2) {
		unix_state_lock(sk1);
		return;
	}
	if (sk1 > sk2)
		swap(sk1, sk2);

	unix_state_lock(sk1);
	unix_state_lock_nested(sk2, U_LOCK_SECOND);
}

static void unix_state_double_unlock(struct sock *sk1, struct sock *sk2)
{
	if (unlikely(sk1 == sk2) || !sk2) {
		unix_state_unlock(sk1);
		return;
	}
	unix_state_unlock(sk1);
	unix_state_unlock(sk2);
}

static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
			      int alen, int flags)
{
	struct sockaddr_un *sunaddr = (struct sockaddr_un *)addr;
	struct sock *sk = sock->sk;
	struct sock *other;
	int err;

	err = -EINVAL;
	if (alen < offsetofend(struct sockaddr, sa_family))
		goto out;

	if (addr->sa_family != AF_UNSPEC) {
		err = unix_validate_addr(sunaddr, alen);
		if (err)
			goto out;

		if ((test_bit(SOCK_PASSCRED, &sock->flags) ||
		     test_bit(SOCK_PASSPIDFD, &sock->flags)) &&
		    !READ_ONCE(unix_sk(sk)->addr)) {
			err = unix_autobind(sk);
			if (err)
				goto out;
		}

restart:
		other = unix_find_other(sock_net(sk), sunaddr, alen, sock->type);
		if (IS_ERR(other)) {
			err = PTR_ERR(other);
			goto out;
		}

		unix_state_double_lock(sk, other);

		/* Apparently VFS overslept socket death. Retry. */
		if (sock_flag(other, SOCK_DEAD)) {
			unix_state_double_unlock(sk, other);
			sock_put(other);
			goto restart;
		}

		err = -EPERM;
		if (!unix_may_send(sk, other))
			goto out_unlock;

		err = security_unix_may_send(sk->sk_socket, other->sk_socket);
		if (err)
			goto out_unlock;

		WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED);
		WRITE_ONCE(other->sk_state, TCP_ESTABLISHED);
	} else {
		/*
		 *	1003.1g breaking connected state with AF_UNSPEC
		 */
		other = NULL;
		unix_state_double_lock(sk, other);
	}

	/*
	 * If it was connected, reconnect.
	 */
	if (unix_peer(sk)) {
		struct sock *old_peer = unix_peer(sk);

		unix_peer(sk) = other;
		if (!other)
			WRITE_ONCE(sk->sk_state, TCP_CLOSE);
		unix_dgram_peer_wake_disconnect_wakeup(sk, old_peer);

		unix_state_double_unlock(sk, other);

		if (other != old_peer) {
			unix_dgram_disconnected(sk, old_peer);

			unix_state_lock(old_peer);
			if (!unix_peer(old_peer))
				WRITE_ONCE(old_peer->sk_state, TCP_CLOSE);
			unix_state_unlock(old_peer);
		}

		sock_put(old_peer);
	} else {
		unix_peer(sk) = other;
		unix_state_double_unlock(sk, other);
	}

	return 0;

out_unlock:
	unix_state_double_unlock(sk, other);
	sock_put(other);
out:
	return err;
}

static long unix_wait_for_peer(struct sock *other, long timeo)
	__releases(&unix_sk(other)->lock)
{
	struct unix_sock *u = unix_sk(other);
	int sched;
	DEFINE_WAIT(wait);

	prepare_to_wait_exclusive(&u->peer_wait, &wait, TASK_INTERRUPTIBLE);

	sched = !sock_flag(other, SOCK_DEAD) &&
		!(other->sk_shutdown & RCV_SHUTDOWN) &&
		unix_recvq_full_lockless(other);

	unix_state_unlock(other);

	if (sched)
		timeo = schedule_timeout(timeo);

	finish_wait(&u->peer_wait, &wait);
	return timeo;
}

static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
			       int addr_len, int flags)
{
	struct sockaddr_un *sunaddr = (struct sockaddr_un *)uaddr;
	struct sock *sk = sock->sk, *newsk = NULL, *other = NULL;
	struct unix_sock *u = unix_sk(sk), *newu, *otheru;
	struct net *net = sock_net(sk);
	struct sk_buff *skb = NULL;
	unsigned char state;
	long timeo;
	int err;

	err = unix_validate_addr(sunaddr, addr_len);
	if (err)
		goto out;

	if ((test_bit(SOCK_PASSCRED, &sock->flags) ||
	     test_bit(SOCK_PASSPIDFD, &sock->flags)) &&
	    !READ_ONCE(u->addr)) {
		err = unix_autobind(sk);
		if (err)
			goto out;
	}

	timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);

	/* First of all allocate resources.
	   If we will make it after state is locked,
	   we will have to recheck all again in any case.
	 */

	/* create new sock for complete connection */
	newsk = unix_create1(net, NULL, 0, sock->type);
	if (IS_ERR(newsk)) {
		err = PTR_ERR(newsk);
		newsk = NULL;
		goto out;
	}

	err = -ENOMEM;

	/* Allocate skb for sending to listening sock */
	skb = sock_wmalloc(newsk, 1, 0, GFP_KERNEL);
	if (skb == NULL)
		goto out;

restart:
	/*  Find listening sock. */
	other = unix_find_other(net, sunaddr, addr_len, sk->sk_type);
	if (IS_ERR(other)) {
		err = PTR_ERR(other);
		other = NULL;
		goto out;
	}

	unix_state_lock(other);

	/* Apparently VFS overslept socket death. Retry. */
	if (sock_flag(other, SOCK_DEAD)) {
		unix_state_unlock(other);
		sock_put(other);
		goto restart;
	}

	err = -ECONNREFUSED;
	if (other->sk_state != TCP_LISTEN)
		goto out_unlock;
	if (other->sk_shutdown & RCV_SHUTDOWN)
		goto out_unlock;

	if (unix_recvq_full_lockless(other)) {
		err = -EAGAIN;
		if (!timeo)
			goto out_unlock;

		timeo = unix_wait_for_peer(other, timeo);

		err = sock_intr_errno(timeo);
		if (signal_pending(current))
			goto out;
		sock_put(other);
		goto restart;
	}

	/* self connect and simultaneous connect are eliminated
	 * by rejecting TCP_LISTEN socket to avoid deadlock.
	 */
	state = READ_ONCE(sk->sk_state);
	if (unlikely(state != TCP_CLOSE)) {
		err = state == TCP_ESTABLISHED ? -EISCONN : -EINVAL;
		goto out_unlock;
	}

	unix_state_lock_nested(sk, U_LOCK_SECOND);

	if (unlikely(sk->sk_state != TCP_CLOSE)) {
		err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EINVAL;
		unix_state_unlock(sk);
		goto out_unlock;
	}

	err = security_unix_stream_connect(sk, other, newsk);
	if (err) {
		unix_state_unlock(sk);
		goto out_unlock;
	}

	/* The way is open! Fastly set all the necessary fields... */

	sock_hold(sk);
	unix_peer(newsk)	= sk;
	newsk->sk_state		= TCP_ESTABLISHED;
	newsk->sk_type		= sk->sk_type;
	init_peercred(newsk);
	newu = unix_sk(newsk);
	RCU_INIT_POINTER(newsk->sk_wq, &newu->peer_wq);
	otheru = unix_sk(other);

	/* copy address information from listening to new sock
	 *
	 * The contents of *(otheru->addr) and otheru->path
	 * are seen fully set up here, since we have found
	 * otheru in hash under its lock.  Insertion into the
	 * hash chain we'd found it in had been done in an
	 * earlier critical area protected by the chain's lock,
	 * the same one where we'd set *(otheru->addr) contents,
	 * as well as otheru->path and otheru->addr itself.
	 *
	 * Using smp_store_release() here to set newu->addr
	 * is enough to make those stores, as well as stores
	 * to newu->path visible to anyone who gets newu->addr
	 * by smp_load_acquire().  IOW, the same warranties
	 * as for unix_sock instances bound in unix_bind() or
	 * in unix_autobind().
	 */
	if (otheru->path.dentry) {
		path_get(&otheru->path);
		newu->path = otheru->path;
	}
	refcount_inc(&otheru->addr->refcnt);
	smp_store_release(&newu->addr, otheru->addr);

	/* Set credentials */
	copy_peercred(sk, other);

	sock->state	= SS_CONNECTED;
	WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED);
	sock_hold(newsk);

	smp_mb__after_atomic();	/* sock_hold() does an atomic_inc() */
	unix_peer(sk)	= newsk;

	unix_state_unlock(sk);

	/* take ten and send info to listening sock */
	spin_lock(&other->sk_receive_queue.lock);
	__skb_queue_tail(&other->sk_receive_queue, skb);
	spin_unlock(&other->sk_receive_queue.lock);
	unix_state_unlock(other);
	other->sk_data_ready(other);
	sock_put(other);
	return 0;

out_unlock:
	if (other)
		unix_state_unlock(other);

out:
	kfree_skb(skb);
	if (newsk)
		unix_release_sock(newsk, 0);
	if (other)
		sock_put(other);
	return err;
}

static int unix_socketpair(struct socket *socka, struct socket *sockb)
{
	struct sock *ska = socka->sk, *skb = sockb->sk;

	/* Join our sockets back to back */
	sock_hold(ska);
	sock_hold(skb);
	unix_peer(ska) = skb;
	unix_peer(skb) = ska;
	init_peercred(ska);
	init_peercred(skb);

	ska->sk_state = TCP_ESTABLISHED;
	skb->sk_state = TCP_ESTABLISHED;
	socka->state  = SS_CONNECTED;
	sockb->state  = SS_CONNECTED;
	return 0;
}

static void unix_sock_inherit_flags(const struct socket *old,
				    struct socket *new)
{
	if (test_bit(SOCK_PASSCRED, &old->flags))
		set_bit(SOCK_PASSCRED, &new->flags);
	if (test_bit(SOCK_PASSPIDFD, &old->flags))
		set_bit(SOCK_PASSPIDFD, &new->flags);
	if (test_bit(SOCK_PASSSEC, &old->flags))
		set_bit(SOCK_PASSSEC, &new->flags);
}

static int unix_accept(struct socket *sock, struct socket *newsock, int flags,
		       bool kern)
{
	struct sock *sk = sock->sk;
	struct sock *tsk;
	struct sk_buff *skb;
	int err;

	err = -EOPNOTSUPP;
	if (sock->type != SOCK_STREAM && sock->type != SOCK_SEQPACKET)
		goto out;

	err = -EINVAL;
	if (READ_ONCE(sk->sk_state) != TCP_LISTEN)
		goto out;

	/* If socket state is TCP_LISTEN it cannot change (for now...),
	 * so that no locks are necessary.
	 */

	skb = skb_recv_datagram(sk, (flags & O_NONBLOCK) ? MSG_DONTWAIT : 0,
				&err);
	if (!skb) {
		/* This means receive shutdown. */
		if (err == 0)
			err = -EINVAL;
		goto out;
	}

	tsk = skb->sk;
	skb_free_datagram(sk, skb);
	wake_up_interruptible(&unix_sk(sk)->peer_wait);

	/* attach accepted sock to socket */
	unix_state_lock(tsk);
	newsock->state = SS_CONNECTED;
	unix_sock_inherit_flags(sock, newsock);
	sock_graft(tsk, newsock);
	unix_state_unlock(tsk);
	return 0;

out:
	return err;
}


static int unix_getname(struct socket *sock, struct sockaddr *uaddr, int peer)
{
	struct sock *sk = sock->sk;
	struct unix_address *addr;
	DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr, uaddr);
	int err = 0;

	if (peer) {
		sk = unix_peer_get(sk);

		err = -ENOTCONN;
		if (!sk)
			goto out;
		err = 0;
	} else {
		sock_hold(sk);
	}

	addr = smp_load_acquire(&unix_sk(sk)->addr);
	if (!addr) {
		sunaddr->sun_family = AF_UNIX;
		sunaddr->sun_path[0] = 0;
		err = offsetof(struct sockaddr_un, sun_path);
	} else {
		err = addr->len;
		memcpy(sunaddr, addr->name, addr->len);
	}
	sock_put(sk);
out:
	return err;
}

static void unix_peek_fds(struct scm_cookie *scm, struct sk_buff *skb)
{
	scm->fp = scm_fp_dup(UNIXCB(skb).fp);

	/*
	 * Garbage collection of unix sockets starts by selecting a set of
	 * candidate sockets which have reference only from being in flight
	 * (total_refs == inflight_refs).  This condition is checked once during
	 * the candidate collection phase, and candidates are marked as such, so
	 * that non-candidates can later be ignored.  While inflight_refs is
	 * protected by unix_gc_lock, total_refs (file count) is not, hence this
	 * is an instantaneous decision.
	 *
	 * Once a candidate, however, the socket must not be reinstalled into a
	 * file descriptor while the garbage collection is in progress.
	 *
	 * If the above conditions are met, then the directed graph of
	 * candidates (*) does not change while unix_gc_lock is held.
	 *
	 * Any operations that changes the file count through file descriptors
	 * (dup, close, sendmsg) does not change the graph since candidates are
	 * not installed in fds.
	 *
	 * Dequeing a candidate via recvmsg would install it into an fd, but
	 * that takes unix_gc_lock to decrement the inflight count, so it's
	 * serialized with garbage collection.
	 *
	 * MSG_PEEK is special in that it does not change the inflight count,
	 * yet does install the socket into an fd.  The following lock/unlock
	 * pair is to ensure serialization with garbage collection.  It must be
	 * done between incrementing the file count and installing the file into
	 * an fd.
	 *
	 * If garbage collection starts after the barrier provided by the
	 * lock/unlock, then it will see the elevated refcount and not mark this
	 * as a candidate.  If a garbage collection is already in progress
	 * before the file count was incremented, then the lock/unlock pair will
	 * ensure that garbage collection is finished before progressing to
	 * installing the fd.
	 *
	 * (*) A -> B where B is on the queue of A or B is on the queue of C
	 * which is on the queue of listening socket A.
	 */
	spin_lock(&unix_gc_lock);
	spin_unlock(&unix_gc_lock);
}

static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool send_fds)
{
	int err = 0;

	UNIXCB(skb).pid  = get_pid(scm->pid);
	UNIXCB(skb).uid = scm->creds.uid;
	UNIXCB(skb).gid = scm->creds.gid;
	UNIXCB(skb).fp = NULL;
	unix_get_secdata(scm, skb);
	if (scm->fp && send_fds)
		err = unix_attach_fds(scm, skb);

	skb->destructor = unix_destruct_scm;
	return err;
}

static bool unix_passcred_enabled(const struct socket *sock,
				  const struct sock *other)
{
	return test_bit(SOCK_PASSCRED, &sock->flags) ||
	       test_bit(SOCK_PASSPIDFD, &sock->flags) ||
	       !other->sk_socket ||
	       test_bit(SOCK_PASSCRED, &other->sk_socket->flags) ||
	       test_bit(SOCK_PASSPIDFD, &other->sk_socket->flags);
}

/*
 * Some apps rely on write() giving SCM_CREDENTIALS
 * We include credentials if source or destination socket
 * asserted SOCK_PASSCRED.
 */
static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
			    const struct sock *other)
{
	if (UNIXCB(skb).pid)
		return;
	if (unix_passcred_enabled(sock, other)) {
		UNIXCB(skb).pid  = get_pid(task_tgid(current));
		current_uid_gid(&UNIXCB(skb).uid, &UNIXCB(skb).gid);
	}
}

static bool unix_skb_scm_eq(struct sk_buff *skb,
			    struct scm_cookie *scm)
{
	return UNIXCB(skb).pid == scm->pid &&
	       uid_eq(UNIXCB(skb).uid, scm->creds.uid) &&
	       gid_eq(UNIXCB(skb).gid, scm->creds.gid) &&
	       unix_secdata_eq(scm, skb);
}

static void scm_stat_add(struct sock *sk, struct sk_buff *skb)
{
	struct scm_fp_list *fp = UNIXCB(skb).fp;
	struct unix_sock *u = unix_sk(sk);

	if (unlikely(fp && fp->count))
		atomic_add(fp->count, &u->scm_stat.nr_fds);
}

static void scm_stat_del(struct sock *sk, struct sk_buff *skb)
{
	struct scm_fp_list *fp = UNIXCB(skb).fp;
	struct unix_sock *u = unix_sk(sk);

	if (unlikely(fp && fp->count))
		atomic_sub(fp->count, &u->scm_stat.nr_fds);
}

/*
 *	Send AF_UNIX data.
 */

static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
			      size_t len)
{
	DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr, msg->msg_name);
	struct sock *sk = sock->sk, *other = NULL;
	struct unix_sock *u = unix_sk(sk);
	struct scm_cookie scm;
	struct sk_buff *skb;
	int data_len = 0;
	int sk_locked;
	long timeo;
	int err;

	wait_for_unix_gc();
	err = scm_send(sock, msg, &scm, false);
	if (err < 0)
		return err;

	err = -EOPNOTSUPP;
	if (msg->msg_flags&MSG_OOB)
		goto out;

	if (msg->msg_namelen) {
		err = unix_validate_addr(sunaddr, msg->msg_namelen);
		if (err)
			goto out;
	} else {
		sunaddr = NULL;
		err = -ENOTCONN;
		other = unix_peer_get(sk);
		if (!other)
			goto out;
	}

	if ((test_bit(SOCK_PASSCRED, &sock->flags) ||
	     test_bit(SOCK_PASSPIDFD, &sock->flags)) &&
	    !READ_ONCE(u->addr)) {
		err = unix_autobind(sk);
		if (err)
			goto out;
	}

	err = -EMSGSIZE;
	if (len > READ_ONCE(sk->sk_sndbuf) - 32)
		goto out;

	if (len > SKB_MAX_ALLOC) {
		data_len = min_t(size_t,
				 len - SKB_MAX_ALLOC,
				 MAX_SKB_FRAGS * PAGE_SIZE);
		data_len = PAGE_ALIGN(data_len);

		BUILD_BUG_ON(SKB_MAX_ALLOC < PAGE_SIZE);
	}

	skb = sock_alloc_send_pskb(sk, len - data_len, data_len,
				   msg->msg_flags & MSG_DONTWAIT, &err,
				   PAGE_ALLOC_COSTLY_ORDER);
	if (skb == NULL)
		goto out;

	err = unix_scm_to_skb(&scm, skb, true);
	if (err < 0)
		goto out_free;

	skb_put(skb, len - data_len);
	skb->data_len = data_len;
	skb->len = len;
	err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, len);
	if (err)
		goto out_free;

	timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);

restart:
	if (!other) {
		err = -ECONNRESET;
		if (sunaddr == NULL)
			goto out_free;

		other = unix_find_other(sock_net(sk), sunaddr, msg->msg_namelen,
					sk->sk_type);
		if (IS_ERR(other)) {
			err = PTR_ERR(other);
			other = NULL;
			goto out_free;
		}
	}

	if (sk_filter(other, skb) < 0) {
		/* Toss the packet but do not return any error to the sender */
		err = len;
		goto out_free;
	}

	sk_locked = 0;
	unix_state_lock(other);
restart_locked:
	err = -EPERM;
	if (!unix_may_send(sk, other))
		goto out_unlock;

	if (unlikely(sock_flag(other, SOCK_DEAD))) {
		/*
		 *	Check with 1003.1g - what should
		 *	datagram error
		 */
		unix_state_unlock(other);
		sock_put(other);

		if (!sk_locked)
			unix_state_lock(sk);

		err = 0;
		if (sk->sk_type == SOCK_SEQPACKET) {
			/* We are here only when racing with unix_release_sock()
			 * is clearing @other. Never change state to TCP_CLOSE
			 * unlike SOCK_DGRAM wants.
			 */
			unix_state_unlock(sk);
			err = -EPIPE;
		} else if (unix_peer(sk) == other) {
			unix_peer(sk) = NULL;
			unix_dgram_peer_wake_disconnect_wakeup(sk, other);

			WRITE_ONCE(sk->sk_state, TCP_CLOSE);
			unix_state_unlock(sk);

			unix_dgram_disconnected(sk, other);
			sock_put(other);
			err = -ECONNREFUSED;
		} else {
			unix_state_unlock(sk);
		}

		other = NULL;
		if (err)
			goto out_free;
		goto restart;
	}

	err = -EPIPE;
	if (other->sk_shutdown & RCV_SHUTDOWN)
		goto out_unlock;

	if (sk->sk_type != SOCK_SEQPACKET) {
		err = security_unix_may_send(sk->sk_socket, other->sk_socket);
		if (err)
			goto out_unlock;
	}

	/* other == sk && unix_peer(other) != sk if
	 * - unix_peer(sk) == NULL, destination address bound to sk
	 * - unix_peer(sk) == sk by time of get but disconnected before lock
	 */
	if (other != sk &&
	    unlikely(unix_peer(other) != sk &&
	    unix_recvq_full_lockless(other))) {
		if (timeo) {
			timeo = unix_wait_for_peer(other, timeo);

			err = sock_intr_errno(timeo);
			if (signal_pending(current))
				goto out_free;

			goto restart;
		}

		if (!sk_locked) {
			unix_state_unlock(other);
			unix_state_double_lock(sk, other);
		}

		if (unix_peer(sk) != other ||
		    unix_dgram_peer_wake_me(sk, other)) {
			err = -EAGAIN;
			sk_locked = 1;
			goto out_unlock;
		}

		if (!sk_locked) {
			sk_locked = 1;
			goto restart_locked;
		}
	}

	if (unlikely(sk_locked))
		unix_state_unlock(sk);

	if (sock_flag(other, SOCK_RCVTSTAMP))
		__net_timestamp(skb);
	maybe_add_creds(skb, sock, other);
	scm_stat_add(other, skb);
	skb_queue_tail(&other->sk_receive_queue, skb);
	unix_state_unlock(other);
	other->sk_data_ready(other);
	sock_put(other);
	scm_destroy(&scm);
	return len;

out_unlock:
	if (sk_locked)
		unix_state_unlock(sk);
	unix_state_unlock(other);
out_free:
	kfree_skb(skb);
out:
	if (other)
		sock_put(other);
	scm_destroy(&scm);
	return err;
}

/* We use paged skbs for stream sockets, and limit occupancy to 32768
 * bytes, and a minimum of a full page.
 */
#define UNIX_SKB_FRAGS_SZ (PAGE_SIZE << get_order(32768))

#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other,
		     struct scm_cookie *scm, bool fds_sent)
{
	struct unix_sock *ousk = unix_sk(other);
	struct sk_buff *skb;
	int err = 0;

	skb = sock_alloc_send_skb(sock->sk, 1, msg->msg_flags & MSG_DONTWAIT, &err);

	if (!skb)
		return err;

	err = unix_scm_to_skb(scm, skb, !fds_sent);
	if (err < 0) {
		kfree_skb(skb);
		return err;
	}
	skb_put(skb, 1);
	err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, 1);

	if (err) {
		kfree_skb(skb);
		return err;
	}

	unix_state_lock(other);

	if (sock_flag(other, SOCK_DEAD) ||
	    (other->sk_shutdown & RCV_SHUTDOWN)) {
		unix_state_unlock(other);
		kfree_skb(skb);
		return -EPIPE;
	}

	maybe_add_creds(skb, sock, other);
	skb_get(skb);

	scm_stat_add(other, skb);

	spin_lock(&other->sk_receive_queue.lock);
	if (ousk->oob_skb)
		consume_skb(ousk->oob_skb);
	WRITE_ONCE(ousk->oob_skb, skb);
	__skb_queue_tail(&other->sk_receive_queue, skb);
	spin_unlock(&other->sk_receive_queue.lock);

	sk_send_sigurg(other);
	unix_state_unlock(other);
	other->sk_data_ready(other);

	return err;
}
#endif

static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
			       size_t len)
{
	struct sock *sk = sock->sk;
	struct sock *other = NULL;
	int err, size;
	struct sk_buff *skb;
	int sent = 0;
	struct scm_cookie scm;
	bool fds_sent = false;
	int data_len;

	wait_for_unix_gc();
	err = scm_send(sock, msg, &scm, false);
	if (err < 0)
		return err;

	err = -EOPNOTSUPP;
	if (msg->msg_flags & MSG_OOB) {
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
		if (len)
			len--;
		else
#endif
			goto out_err;
	}

	if (msg->msg_namelen) {
		err = READ_ONCE(sk->sk_state) == TCP_ESTABLISHED ? -EISCONN : -EOPNOTSUPP;
		goto out_err;
	} else {
		err = -ENOTCONN;
		other = unix_peer(sk);
		if (!other)
			goto out_err;
	}

	if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
		goto pipe_err;

	while (sent < len) {
		size = len - sent;

		if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) {
			skb = sock_alloc_send_pskb(sk, 0, 0,
						   msg->msg_flags & MSG_DONTWAIT,
						   &err, 0);
		} else {
			/* Keep two messages in the pipe so it schedules better */
			size = min_t(int, size, (READ_ONCE(sk->sk_sndbuf) >> 1) - 64);

			/* allow fallback to order-0 allocations */
			size = min_t(int, size, SKB_MAX_HEAD(0) + UNIX_SKB_FRAGS_SZ);

			data_len = max_t(int, 0, size - SKB_MAX_HEAD(0));

			data_len = min_t(size_t, size, PAGE_ALIGN(data_len));

			skb = sock_alloc_send_pskb(sk, size - data_len, data_len,
						   msg->msg_flags & MSG_DONTWAIT, &err,
						   get_order(UNIX_SKB_FRAGS_SZ));
		}
		if (!skb)
			goto out_err;

		/* Only send the fds in the first buffer */
		err = unix_scm_to_skb(&scm, skb, !fds_sent);
		if (err < 0) {
			kfree_skb(skb);
			goto out_err;
		}
		fds_sent = true;

		if (unlikely(msg->msg_flags & MSG_SPLICE_PAGES)) {
			err = skb_splice_from_iter(skb, &msg->msg_iter, size,
						   sk->sk_allocation);
			if (err < 0) {
				kfree_skb(skb);
				goto out_err;
			}
			size = err;
			refcount_add(size, &sk->sk_wmem_alloc);
		} else {
			skb_put(skb, size - data_len);
			skb->data_len = data_len;
			skb->len = size;
			err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, size);
			if (err) {
				kfree_skb(skb);
				goto out_err;
			}
		}

		unix_state_lock(other);

		if (sock_flag(other, SOCK_DEAD) ||
		    (other->sk_shutdown & RCV_SHUTDOWN))
			goto pipe_err_free;

		maybe_add_creds(skb, sock, other);
		scm_stat_add(other, skb);
		skb_queue_tail(&other->sk_receive_queue, skb);
		unix_state_unlock(other);
		other->sk_data_ready(other);
		sent += size;
	}

#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
	if (msg->msg_flags & MSG_OOB) {
		err = queue_oob(sock, msg, other, &scm, fds_sent);
		if (err)
			goto out_err;
		sent++;
	}
#endif

	scm_destroy(&scm);

	return sent;

pipe_err_free:
	unix_state_unlock(other);
	kfree_skb(skb);
pipe_err:
	if (sent == 0 && !(msg->msg_flags&MSG_NOSIGNAL))
		send_sig(SIGPIPE, current, 0);
	err = -EPIPE;
out_err:
	scm_destroy(&scm);
	return sent ? : err;
}

static int unix_seqpacket_sendmsg(struct socket *sock, struct msghdr *msg,
				  size_t len)
{
	int err;
	struct sock *sk = sock->sk;

	err = sock_error(sk);
	if (err)
		return err;

	if (READ_ONCE(sk->sk_state) != TCP_ESTABLISHED)
		return -ENOTCONN;

	if (msg->msg_namelen)
		msg->msg_namelen = 0;

	return unix_dgram_sendmsg(sock, msg, len);
}

static int unix_seqpacket_recvmsg(struct socket *sock, struct msghdr *msg,
				  size_t size, int flags)
{
	struct sock *sk = sock->sk;

	if (READ_ONCE(sk->sk_state) != TCP_ESTABLISHED)
		return -ENOTCONN;

	return unix_dgram_recvmsg(sock, msg, size, flags);
}

static void unix_copy_addr(struct msghdr *msg, struct sock *sk)
{
	struct unix_address *addr = smp_load_acquire(&unix_sk(sk)->addr);

	if (addr) {
		msg->msg_namelen = addr->len;
		memcpy(msg->msg_name, addr->name, addr->len);
	}
}

int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
			 int flags)
{
	struct scm_cookie scm;
	struct socket *sock = sk->sk_socket;
	struct unix_sock *u = unix_sk(sk);
	struct sk_buff *skb, *last;
	long timeo;
	int skip;
	int err;

	err = -EOPNOTSUPP;
	if (flags&MSG_OOB)
		goto out;

	timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);

	do {
		mutex_lock(&u->iolock);

		skip = sk_peek_offset(sk, flags);
		skb = __skb_try_recv_datagram(sk, &sk->sk_receive_queue, flags,
					      &skip, &err, &last);
		if (skb) {
			if (!(flags & MSG_PEEK))
				scm_stat_del(sk, skb);
			break;
		}

		mutex_unlock(&u->iolock);

		if (err != -EAGAIN)
			break;
	} while (timeo &&
		 !__skb_wait_for_more_packets(sk, &sk->sk_receive_queue,
					      &err, &timeo, last));

	if (!skb) { /* implies iolock unlocked */
		unix_state_lock(sk);
		/* Signal EOF on disconnected non-blocking SEQPACKET socket. */
		if (sk->sk_type == SOCK_SEQPACKET && err == -EAGAIN &&
		    (sk->sk_shutdown & RCV_SHUTDOWN))
			err = 0;
		unix_state_unlock(sk);
		goto out;
	}

	if (wq_has_sleeper(&u->peer_wait))
		wake_up_interruptible_sync_poll(&u->peer_wait,
						EPOLLOUT | EPOLLWRNORM |
						EPOLLWRBAND);

	if (msg->msg_name)
		unix_copy_addr(msg, skb->sk);

	if (size > skb->len - skip)
		size = skb->len - skip;
	else if (size < skb->len - skip)
		msg->msg_flags |= MSG_TRUNC;

	err = skb_copy_datagram_msg(skb, skip, msg, size);
	if (err)
		goto out_free;

	if (sock_flag(sk, SOCK_RCVTSTAMP))
		__sock_recv_timestamp(msg, sk, skb);

	memset(&scm, 0, sizeof(scm));

	scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
	unix_set_secdata(&scm, skb);

	if (!(flags & MSG_PEEK)) {
		if (UNIXCB(skb).fp)
			unix_detach_fds(&scm, skb);

		sk_peek_offset_bwd(sk, skb->len);
	} else {
		/* It is questionable: on PEEK we could:
		   - do not return fds - good, but too simple 8)
		   - return fds, and do not return them on read (old strategy,
		     apparently wrong)
		   - clone fds (I chose it for now, it is the most universal
		     solution)

		   POSIX 1003.1g does not actually define this clearly
		   at all. POSIX 1003.1g doesn't define a lot of things
		   clearly however!

		*/

		sk_peek_offset_fwd(sk, size);

		if (UNIXCB(skb).fp)
			unix_peek_fds(&scm, skb);
	}
	err = (flags & MSG_TRUNC) ? skb->len - skip : size;

	scm_recv_unix(sock, msg, &scm, flags);

out_free:
	skb_free_datagram(sk, skb);
	mutex_unlock(&u->iolock);
out:
	return err;
}

static int unix_dgram_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
			      int flags)
{
	struct sock *sk = sock->sk;

#ifdef CONFIG_BPF_SYSCALL
	const struct proto *prot = READ_ONCE(sk->sk_prot);

	if (prot != &unix_dgram_proto)
		return prot->recvmsg(sk, msg, size, flags, NULL);
#endif
	return __unix_dgram_recvmsg(sk, msg, size, flags);
}

static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
{
	struct unix_sock *u = unix_sk(sk);
	struct sk_buff *skb;
	int err;

	mutex_lock(&u->iolock);
	skb = skb_recv_datagram(sk, MSG_DONTWAIT, &err);
	mutex_unlock(&u->iolock);
	if (!skb)
		return err;

	return recv_actor(sk, skb);
}

/*
 *	Sleep until more data has arrived. But check for races..
 */
static long unix_stream_data_wait(struct sock *sk, long timeo,
				  struct sk_buff *last, unsigned int last_len,
				  bool freezable)
{
	unsigned int state = TASK_INTERRUPTIBLE | freezable * TASK_FREEZABLE;
	struct sk_buff *tail;
	DEFINE_WAIT(wait);

	unix_state_lock(sk);

	for (;;) {
		prepare_to_wait(sk_sleep(sk), &wait, state);

		tail = skb_peek_tail(&sk->sk_receive_queue);
		if (tail != last ||
		    (tail && tail->len != last_len) ||
		    sk->sk_err ||
		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
		    signal_pending(current) ||
		    !timeo)
			break;

		sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
		unix_state_unlock(sk);
		timeo = schedule_timeout(timeo);
		unix_state_lock(sk);

		if (sock_flag(sk, SOCK_DEAD))
			break;

		sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
	}

	finish_wait(sk_sleep(sk), &wait);
	unix_state_unlock(sk);
	return timeo;
}

static unsigned int unix_skb_len(const struct sk_buff *skb)
{
	return skb->len - UNIXCB(skb).consumed;
}

struct unix_stream_read_state {
	int (*recv_actor)(struct sk_buff *, int, int,
			  struct unix_stream_read_state *);
	struct socket *socket;
	struct msghdr *msg;
	struct pipe_inode_info *pipe;
	size_t size;
	int flags;
	unsigned int splice_flags;
};

#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
static int unix_stream_recv_urg(struct unix_stream_read_state *state)
{
	struct socket *sock = state->socket;
	struct sock *sk = sock->sk;
	struct unix_sock *u = unix_sk(sk);
	int chunk = 1;
	struct sk_buff *oob_skb;

	mutex_lock(&u->iolock);
	unix_state_lock(sk);
	spin_lock(&sk->sk_receive_queue.lock);

	if (sock_flag(sk, SOCK_URGINLINE) || !u->oob_skb) {
		spin_unlock(&sk->sk_receive_queue.lock);
		unix_state_unlock(sk);
		mutex_unlock(&u->iolock);
		return -EINVAL;
	}

	oob_skb = u->oob_skb;

	if (!(state->flags & MSG_PEEK))
		WRITE_ONCE(u->oob_skb, NULL);
	else
		skb_get(oob_skb);

	spin_unlock(&sk->sk_receive_queue.lock);
	unix_state_unlock(sk);

	chunk = state->recv_actor(oob_skb, 0, chunk, state);

	if (!(state->flags & MSG_PEEK))
		UNIXCB(oob_skb).consumed += 1;

	consume_skb(oob_skb);

	mutex_unlock(&u->iolock);

	if (chunk < 0)
		return -EFAULT;

	state->msg->msg_flags |= MSG_OOB;
	return 1;
}

static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
				  int flags, int copied)
{
	struct unix_sock *u = unix_sk(sk);

	if (!unix_skb_len(skb) && !(flags & MSG_PEEK)) {
		skb_unlink(skb, &sk->sk_receive_queue);
		consume_skb(skb);
		skb = NULL;
	} else {
		struct sk_buff *unlinked_skb = NULL;

		spin_lock(&sk->sk_receive_queue.lock);

		if (skb == u->oob_skb) {
			if (copied) {
				skb = NULL;
			} else if (!(flags & MSG_PEEK)) {
				if (sock_flag(sk, SOCK_URGINLINE)) {
					WRITE_ONCE(u->oob_skb, NULL);
					consume_skb(skb);
				} else {
					__skb_unlink(skb, &sk->sk_receive_queue);
					WRITE_ONCE(u->oob_skb, NULL);
					unlinked_skb = skb;
					skb = skb_peek(&sk->sk_receive_queue);
				}
			} else if (!sock_flag(sk, SOCK_URGINLINE)) {
				skb = skb_peek_next(skb, &sk->sk_receive_queue);
			}
		}

		spin_unlock(&sk->sk_receive_queue.lock);

		if (unlinked_skb) {
			WARN_ON_ONCE(skb_unref(unlinked_skb));
			kfree_skb(unlinked_skb);
		}
	}
	return skb;
}
#endif

static int unix_stream_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
{
	struct unix_sock *u = unix_sk(sk);
	struct sk_buff *skb;
	int err;

	if (unlikely(READ_ONCE(sk->sk_state) != TCP_ESTABLISHED))
		return -ENOTCONN;

	mutex_lock(&u->iolock);
	skb = skb_recv_datagram(sk, MSG_DONTWAIT, &err);
	mutex_unlock(&u->iolock);
	if (!skb)
		return err;

#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
	if (unlikely(skb == READ_ONCE(u->oob_skb))) {
		bool drop = false;

		unix_state_lock(sk);

		if (sock_flag(sk, SOCK_DEAD)) {
			unix_state_unlock(sk);
			kfree_skb(skb);
			return -ECONNRESET;
		}

		spin_lock(&sk->sk_receive_queue.lock);
		if (likely(skb == u->oob_skb)) {
			WRITE_ONCE(u->oob_skb, NULL);
			drop = true;
		}
		spin_unlock(&sk->sk_receive_queue.lock);

		unix_state_unlock(sk);

		if (drop) {
			WARN_ON_ONCE(skb_unref(skb));
			kfree_skb(skb);
			return -EAGAIN;
		}
	}
#endif

	return recv_actor(sk, skb);
}

static int unix_stream_read_generic(struct unix_stream_read_state *state,
				    bool freezable)
{
	struct scm_cookie scm;
	struct socket *sock = state->socket;
	struct sock *sk = sock->sk;
	struct unix_sock *u = unix_sk(sk);
	int copied = 0;
	int flags = state->flags;
	int noblock = flags & MSG_DONTWAIT;
	bool check_creds = false;
	int target;
	int err = 0;
	long timeo;
	int skip;
	size_t size = state->size;
	unsigned int last_len;

	if (unlikely(READ_ONCE(sk->sk_state) != TCP_ESTABLISHED)) {
		err = -EINVAL;
		goto out;
	}

	if (unlikely(flags & MSG_OOB)) {
		err = -EOPNOTSUPP;
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
		err = unix_stream_recv_urg(state);
#endif
		goto out;
	}

	target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
	timeo = sock_rcvtimeo(sk, noblock);

	memset(&scm, 0, sizeof(scm));

	/* Lock the socket to prevent queue disordering
	 * while sleeps in memcpy_tomsg
	 */
	mutex_lock(&u->iolock);

	skip = max(sk_peek_offset(sk, flags), 0);

	do {
		int chunk;
		bool drop_skb;
		struct sk_buff *skb, *last;

redo:
		unix_state_lock(sk);
		if (sock_flag(sk, SOCK_DEAD)) {
			err = -ECONNRESET;
			goto unlock;
		}
		last = skb = skb_peek(&sk->sk_receive_queue);
		last_len = last ? last->len : 0;

again:
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
		if (skb) {
			skb = manage_oob(skb, sk, flags, copied);
			if (!skb && copied) {
				unix_state_unlock(sk);
				break;
			}
		}
#endif
		if (skb == NULL) {
			if (copied >= target)
				goto unlock;

			/*
			 *	POSIX 1003.1g mandates this order.
			 */

			err = sock_error(sk);
			if (err)
				goto unlock;
			if (sk->sk_shutdown & RCV_SHUTDOWN)
				goto unlock;

			unix_state_unlock(sk);
			if (!timeo) {
				err = -EAGAIN;
				break;
			}

			mutex_unlock(&u->iolock);

			timeo = unix_stream_data_wait(sk, timeo, last,
						      last_len, freezable);

			if (signal_pending(current)) {
				err = sock_intr_errno(timeo);
				scm_destroy(&scm);
				goto out;
			}

			mutex_lock(&u->iolock);
			goto redo;
unlock:
			unix_state_unlock(sk);
			break;
		}

		while (skip >= unix_skb_len(skb)) {
			skip -= unix_skb_len(skb);
			last = skb;
			last_len = skb->len;
			skb = skb_peek_next(skb, &sk->sk_receive_queue);
			if (!skb)
				goto again;
		}

		unix_state_unlock(sk);

		if (check_creds) {
			/* Never glue messages from different writers */
			if (!unix_skb_scm_eq(skb, &scm))
				break;
		} else if (test_bit(SOCK_PASSCRED, &sock->flags) ||
			   test_bit(SOCK_PASSPIDFD, &sock->flags)) {
			/* Copy credentials */
			scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
			unix_set_secdata(&scm, skb);
			check_creds = true;
		}

		/* Copy address just once */
		if (state->msg && state->msg->msg_name) {
			DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr,
					 state->msg->msg_name);
			unix_copy_addr(state->msg, skb->sk);
			sunaddr = NULL;
		}

		chunk = min_t(unsigned int, unix_skb_len(skb) - skip, size);
		skb_get(skb);
		chunk = state->recv_actor(skb, skip, chunk, state);
		drop_skb = !unix_skb_len(skb);
		/* skb is only safe to use if !drop_skb */
		consume_skb(skb);
		if (chunk < 0) {
			if (copied == 0)
				copied = -EFAULT;
			break;
		}
		copied += chunk;
		size -= chunk;

		if (drop_skb) {
			/* the skb was touched by a concurrent reader;
			 * we should not expect anything from this skb
			 * anymore and assume it invalid - we can be
			 * sure it was dropped from the socket queue
			 *
			 * let's report a short read
			 */
			err = 0;
			break;
		}

		/* Mark read part of skb as used */
		if (!(flags & MSG_PEEK)) {
			UNIXCB(skb).consumed += chunk;

			sk_peek_offset_bwd(sk, chunk);

			if (UNIXCB(skb).fp) {
				scm_stat_del(sk, skb);
				unix_detach_fds(&scm, skb);
			}

			if (unix_skb_len(skb))
				break;

			skb_unlink(skb, &sk->sk_receive_queue);
			consume_skb(skb);

			if (scm.fp)
				break;
		} else {
			/* It is questionable, see note in unix_dgram_recvmsg.
			 */
			if (UNIXCB(skb).fp)
				unix_peek_fds(&scm, skb);

			sk_peek_offset_fwd(sk, chunk);

			if (UNIXCB(skb).fp)
				break;

			skip = 0;
			last = skb;
			last_len = skb->len;
			unix_state_lock(sk);
			skb = skb_peek_next(skb, &sk->sk_receive_queue);
			if (skb)
				goto again;
			unix_state_unlock(sk);
			break;
		}
	} while (size);

	mutex_unlock(&u->iolock);
	if (state->msg)
		scm_recv_unix(sock, state->msg, &scm, flags);
	else
		scm_destroy(&scm);
out:
	return copied ? : err;
}

static int unix_stream_read_actor(struct sk_buff *skb,
				  int skip, int chunk,
				  struct unix_stream_read_state *state)
{
	int ret;

	ret = skb_copy_datagram_msg(skb, UNIXCB(skb).consumed + skip,
				    state->msg, chunk);
	return ret ?: chunk;
}

int __unix_stream_recvmsg(struct sock *sk, struct msghdr *msg,
			  size_t size, int flags)
{
	struct unix_stream_read_state state = {
		.recv_actor = unix_stream_read_actor,
		.socket = sk->sk_socket,
		.msg = msg,
		.size = size,
		.flags = flags
	};

	return unix_stream_read_generic(&state, true);
}

static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
			       size_t size, int flags)
{
	struct unix_stream_read_state state = {
		.recv_actor = unix_stream_read_actor,
		.socket = sock,
		.msg = msg,
		.size = size,
		.flags = flags
	};

#ifdef CONFIG_BPF_SYSCALL
	struct sock *sk = sock->sk;
	const struct proto *prot = READ_ONCE(sk->sk_prot);

	if (prot != &unix_stream_proto)
		return prot->recvmsg(sk, msg, size, flags, NULL);
#endif
	return unix_stream_read_generic(&state, true);
}

static int unix_stream_splice_actor(struct sk_buff *skb,
				    int skip, int chunk,
				    struct unix_stream_read_state *state)
{
	return skb_splice_bits(skb, state->socket->sk,
			       UNIXCB(skb).consumed + skip,
			       state->pipe, chunk, state->splice_flags);
}

static ssize_t unix_stream_splice_read(struct socket *sock,  loff_t *ppos,
				       struct pipe_inode_info *pipe,
				       size_t size, unsigned int flags)
{
	struct unix_stream_read_state state = {
		.recv_actor = unix_stream_splice_actor,
		.socket = sock,
		.pipe = pipe,
		.size = size,
		.splice_flags = flags,
	};

	if (unlikely(*ppos))
		return -ESPIPE;

	if (sock->file->f_flags & O_NONBLOCK ||
	    flags & SPLICE_F_NONBLOCK)
		state.flags = MSG_DONTWAIT;

	return unix_stream_read_generic(&state, false);
}

static int unix_shutdown(struct socket *sock, int mode)
{
	struct sock *sk = sock->sk;
	struct sock *other;

	if (mode < SHUT_RD || mode > SHUT_RDWR)
		return -EINVAL;
	/* This maps:
	 * SHUT_RD   (0) -> RCV_SHUTDOWN  (1)
	 * SHUT_WR   (1) -> SEND_SHUTDOWN (2)
	 * SHUT_RDWR (2) -> SHUTDOWN_MASK (3)
	 */
	++mode;

	unix_state_lock(sk);
	WRITE_ONCE(sk->sk_shutdown, sk->sk_shutdown | mode);
	other = unix_peer(sk);
	if (other)
		sock_hold(other);
	unix_state_unlock(sk);
	sk->sk_state_change(sk);

	if (other &&
		(sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)) {

		int peer_mode = 0;
		const struct proto *prot = READ_ONCE(other->sk_prot);

		if (prot->unhash)
			prot->unhash(other);
		if (mode&RCV_SHUTDOWN)
			peer_mode |= SEND_SHUTDOWN;
		if (mode&SEND_SHUTDOWN)
			peer_mode |= RCV_SHUTDOWN;
		unix_state_lock(other);
		WRITE_ONCE(other->sk_shutdown, other->sk_shutdown | peer_mode);
		unix_state_unlock(other);
		other->sk_state_change(other);
		if (peer_mode == SHUTDOWN_MASK)
			sk_wake_async(other, SOCK_WAKE_WAITD, POLL_HUP);
		else if (peer_mode & RCV_SHUTDOWN)
			sk_wake_async(other, SOCK_WAKE_WAITD, POLL_IN);
	}
	if (other)
		sock_put(other);

	return 0;
}

long unix_inq_len(struct sock *sk)
{
	struct sk_buff *skb;
	long amount = 0;

	if (READ_ONCE(sk->sk_state) == TCP_LISTEN)
		return -EINVAL;

	spin_lock(&sk->sk_receive_queue.lock);
	if (sk->sk_type == SOCK_STREAM ||
	    sk->sk_type == SOCK_SEQPACKET) {
		skb_queue_walk(&sk->sk_receive_queue, skb)
			amount += unix_skb_len(skb);
	} else {
		skb = skb_peek(&sk->sk_receive_queue);
		if (skb)
			amount = skb->len;
	}
	spin_unlock(&sk->sk_receive_queue.lock);

	return amount;
}
EXPORT_SYMBOL_GPL(unix_inq_len);

long unix_outq_len(struct sock *sk)
{
	return sk_wmem_alloc_get(sk);
}
EXPORT_SYMBOL_GPL(unix_outq_len);

static int unix_open_file(struct sock *sk)
{
	struct path path;
	struct file *f;
	int fd;

	if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
		return -EPERM;

	if (!smp_load_acquire(&unix_sk(sk)->addr))
		return -ENOENT;

	path = unix_sk(sk)->path;
	if (!path.dentry)
		return -ENOENT;

	path_get(&path);

	fd = get_unused_fd_flags(O_CLOEXEC);
	if (fd < 0)
		goto out;

	f = dentry_open(&path, O_PATH, current_cred());
	if (IS_ERR(f)) {
		put_unused_fd(fd);
		fd = PTR_ERR(f);
		goto out;
	}

	fd_install(fd, f);
out:
	path_put(&path);

	return fd;
}

static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
	struct sock *sk = sock->sk;
	long amount = 0;
	int err;

	switch (cmd) {
	case SIOCOUTQ:
		amount = unix_outq_len(sk);
		err = put_user(amount, (int __user *)arg);
		break;
	case SIOCINQ:
		amount = unix_inq_len(sk);
		if (amount < 0)
			err = amount;
		else
			err = put_user(amount, (int __user *)arg);
		break;
	case SIOCUNIXFILE:
		err = unix_open_file(sk);
		break;
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
	case SIOCATMARK:
		{
			struct sk_buff *skb;
			int answ = 0;

			skb = skb_peek(&sk->sk_receive_queue);
			if (skb && skb == READ_ONCE(unix_sk(sk)->oob_skb))
				answ = 1;
			err = put_user(answ, (int __user *)arg);
		}
		break;
#endif
	default:
		err = -ENOIOCTLCMD;
		break;
	}
	return err;
}

#ifdef CONFIG_COMPAT
static int unix_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
	return unix_ioctl(sock, cmd, (unsigned long)compat_ptr(arg));
}
#endif

static __poll_t unix_poll(struct file *file, struct socket *sock, poll_table *wait)
{
	struct sock *sk = sock->sk;
	unsigned char state;
	__poll_t mask;
	u8 shutdown;

	sock_poll_wait(file, sock, wait);
	mask = 0;
	shutdown = READ_ONCE(sk->sk_shutdown);
	state = READ_ONCE(sk->sk_state);

	/* exceptional events? */
	if (READ_ONCE(sk->sk_err))
		mask |= EPOLLERR;
	if (shutdown == SHUTDOWN_MASK)
		mask |= EPOLLHUP;
	if (shutdown & RCV_SHUTDOWN)
		mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;

	/* readable? */
	if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
		mask |= EPOLLIN | EPOLLRDNORM;
	if (sk_is_readable(sk))
		mask |= EPOLLIN | EPOLLRDNORM;
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
	if (READ_ONCE(unix_sk(sk)->oob_skb))
		mask |= EPOLLPRI;
#endif

	/* Connection-based need to check for termination and startup */
	if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) &&
	    state == TCP_CLOSE)
		mask |= EPOLLHUP;

	/*
	 * we set writable also when the other side has shut down the
	 * connection. This prevents stuck sockets.
	 */
	if (unix_writable(sk, state))
		mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;

	return mask;
}

static __poll_t unix_dgram_poll(struct file *file, struct socket *sock,
				    poll_table *wait)
{
	struct sock *sk = sock->sk, *other;
	unsigned int writable;
	unsigned char state;
	__poll_t mask;
	u8 shutdown;

	sock_poll_wait(file, sock, wait);
	mask = 0;
	shutdown = READ_ONCE(sk->sk_shutdown);
	state = READ_ONCE(sk->sk_state);

	/* exceptional events? */
	if (READ_ONCE(sk->sk_err) ||
	    !skb_queue_empty_lockless(&sk->sk_error_queue))
		mask |= EPOLLERR |
			(sock_flag(sk, SOCK_SELECT_ERR_QUEUE) ? EPOLLPRI : 0);

	if (shutdown & RCV_SHUTDOWN)
		mask |= EPOLLRDHUP | EPOLLIN | EPOLLRDNORM;
	if (shutdown == SHUTDOWN_MASK)
		mask |= EPOLLHUP;

	/* readable? */
	if (!skb_queue_empty_lockless(&sk->sk_receive_queue))
		mask |= EPOLLIN | EPOLLRDNORM;
	if (sk_is_readable(sk))
		mask |= EPOLLIN | EPOLLRDNORM;

	/* Connection-based need to check for termination and startup */
	if (sk->sk_type == SOCK_SEQPACKET && state == TCP_CLOSE)
		mask |= EPOLLHUP;

	/* No write status requested, avoid expensive OUT tests. */
	if (!(poll_requested_events(wait) & (EPOLLWRBAND|EPOLLWRNORM|EPOLLOUT)))
		return mask;

	writable = unix_writable(sk, state);
	if (writable) {
		unix_state_lock(sk);

		other = unix_peer(sk);
		if (other && unix_peer(other) != sk &&
		    unix_recvq_full_lockless(other) &&
		    unix_dgram_peer_wake_me(sk, other))
			writable = 0;

		unix_state_unlock(sk);
	}

	if (writable)
		mask |= EPOLLOUT | EPOLLWRNORM | EPOLLWRBAND;
	else
		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);

	return mask;
}

#ifdef CONFIG_PROC_FS

#define BUCKET_SPACE (BITS_PER_LONG - (UNIX_HASH_BITS + 1) - 1)

#define get_bucket(x) ((x) >> BUCKET_SPACE)
#define get_offset(x) ((x) & ((1UL << BUCKET_SPACE) - 1))
#define set_bucket_offset(b, o) ((b) << BUCKET_SPACE | (o))

static struct sock *unix_from_bucket(struct seq_file *seq, loff_t *pos)
{
	unsigned long offset = get_offset(*pos);
	unsigned long bucket = get_bucket(*pos);
	unsigned long count = 0;
	struct sock *sk;

	for (sk = sk_head(&seq_file_net(seq)->unx.table.buckets[bucket]);
	     sk; sk = sk_next(sk)) {
		if (++count == offset)
			break;
	}

	return sk;
}

static struct sock *unix_get_first(struct seq_file *seq, loff_t *pos)
{
	unsigned long bucket = get_bucket(*pos);
	struct net *net = seq_file_net(seq);
	struct sock *sk;

	while (bucket < UNIX_HASH_SIZE) {
		spin_lock(&net->unx.table.locks[bucket]);

		sk = unix_from_bucket(seq, pos);
		if (sk)
			return sk;

		spin_unlock(&net->unx.table.locks[bucket]);

		*pos = set_bucket_offset(++bucket, 1);
	}

	return NULL;
}

static struct sock *unix_get_next(struct seq_file *seq, struct sock *sk,
				  loff_t *pos)
{
	unsigned long bucket = get_bucket(*pos);

	sk = sk_next(sk);
	if (sk)
		return sk;


	spin_unlock(&seq_file_net(seq)->unx.table.locks[bucket]);

	*pos = set_bucket_offset(++bucket, 1);

	return unix_get_first(seq, pos);
}

static void *unix_seq_start(struct seq_file *seq, loff_t *pos)
{
	if (!*pos)
		return SEQ_START_TOKEN;

	return unix_get_first(seq, pos);
}

static void *unix_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	++*pos;

	if (v == SEQ_START_TOKEN)
		return unix_get_first(seq, pos);

	return unix_get_next(seq, v, pos);
}

static void unix_seq_stop(struct seq_file *seq, void *v)
{
	struct sock *sk = v;

	if (sk)
		spin_unlock(&seq_file_net(seq)->unx.table.locks[sk->sk_hash]);
}

static int unix_seq_show(struct seq_file *seq, void *v)
{

	if (v == SEQ_START_TOKEN)
		seq_puts(seq, "Num       RefCount Protocol Flags    Type St "
			 "Inode Path\n");
	else {
		struct sock *s = v;
		struct unix_sock *u = unix_sk(s);
		unix_state_lock(s);

		seq_printf(seq, "%pK: %08X %08X %08X %04X %02X %5lu",
			s,
			refcount_read(&s->sk_refcnt),
			0,
			s->sk_state == TCP_LISTEN ? __SO_ACCEPTCON : 0,
			s->sk_type,
			s->sk_socket ?
			(s->sk_state == TCP_ESTABLISHED ? SS_CONNECTED : SS_UNCONNECTED) :
			(s->sk_state == TCP_ESTABLISHED ? SS_CONNECTING : SS_DISCONNECTING),
			sock_i_ino(s));

		if (u->addr) {	// under a hash table lock here
			int i, len;
			seq_putc(seq, ' ');

			i = 0;
			len = u->addr->len -
				offsetof(struct sockaddr_un, sun_path);
			if (u->addr->name->sun_path[0]) {
				len--;
			} else {
				seq_putc(seq, '@');
				i++;
			}
			for ( ; i < len; i++)
				seq_putc(seq, u->addr->name->sun_path[i] ?:
					 '@');
		}
		unix_state_unlock(s);
		seq_putc(seq, '\n');
	}

	return 0;
}

static const struct seq_operations unix_seq_ops = {
	.start  = unix_seq_start,
	.next   = unix_seq_next,
	.stop   = unix_seq_stop,
	.show   = unix_seq_show,
};

#if IS_BUILTIN(CONFIG_UNIX) && defined(CONFIG_BPF_SYSCALL)
struct bpf_unix_iter_state {
	struct seq_net_private p;
	unsigned int cur_sk;
	unsigned int end_sk;
	unsigned int max_sk;
	struct sock **batch;
	bool st_bucket_done;
};

struct bpf_iter__unix {
	__bpf_md_ptr(struct bpf_iter_meta *, meta);
	__bpf_md_ptr(struct unix_sock *, unix_sk);
	uid_t uid __aligned(8);
};

static int unix_prog_seq_show(struct bpf_prog *prog, struct bpf_iter_meta *meta,
			      struct unix_sock *unix_sk, uid_t uid)
{
	struct bpf_iter__unix ctx;

	meta->seq_num--;  /* skip SEQ_START_TOKEN */
	ctx.meta = meta;
	ctx.unix_sk = unix_sk;
	ctx.uid = uid;
	return bpf_iter_run_prog(prog, &ctx);
}

static int bpf_iter_unix_hold_batch(struct seq_file *seq, struct sock *start_sk)

{
	struct bpf_unix_iter_state *iter = seq->private;
	unsigned int expected = 1;
	struct sock *sk;

	sock_hold(start_sk);
	iter->batch[iter->end_sk++] = start_sk;

	for (sk = sk_next(start_sk); sk; sk = sk_next(sk)) {
		if (iter->end_sk < iter->max_sk) {
			sock_hold(sk);
			iter->batch[iter->end_sk++] = sk;
		}

		expected++;
	}

	spin_unlock(&seq_file_net(seq)->unx.table.locks[start_sk->sk_hash]);

	return expected;
}

static void bpf_iter_unix_put_batch(struct bpf_unix_iter_state *iter)
{
	while (iter->cur_sk < iter->end_sk)
		sock_put(iter->batch[iter->cur_sk++]);
}

static int bpf_iter_unix_realloc_batch(struct bpf_unix_iter_state *iter,
				       unsigned int new_batch_sz)
{
	struct sock **new_batch;

	new_batch = kvmalloc(sizeof(*new_batch) * new_batch_sz,
			     GFP_USER | __GFP_NOWARN);
	if (!new_batch)
		return -ENOMEM;

	bpf_iter_unix_put_batch(iter);
	kvfree(iter->batch);
	iter->batch = new_batch;
	iter->max_sk = new_batch_sz;

	return 0;
}

static struct sock *bpf_iter_unix_batch(struct seq_file *seq,
					loff_t *pos)
{
	struct bpf_unix_iter_state *iter = seq->private;
	unsigned int expected;
	bool resized = false;
	struct sock *sk;

	if (iter->st_bucket_done)
		*pos = set_bucket_offset(get_bucket(*pos) + 1, 1);

again:
	/* Get a new batch */
	iter->cur_sk = 0;
	iter->end_sk = 0;

	sk = unix_get_first(seq, pos);
	if (!sk)
		return NULL; /* Done */

	expected = bpf_iter_unix_hold_batch(seq, sk);

	if (iter->end_sk == expected) {
		iter->st_bucket_done = true;
		return sk;
	}

	if (!resized && !bpf_iter_unix_realloc_batch(iter, expected * 3 / 2)) {
		resized = true;
		goto again;
	}

	return sk;
}

static void *bpf_iter_unix_seq_start(struct seq_file *seq, loff_t *pos)
{
	if (!*pos)
		return SEQ_START_TOKEN;

	/* bpf iter does not support lseek, so it always
	 * continue from where it was stop()-ped.
	 */
	return bpf_iter_unix_batch(seq, pos);
}

static void *bpf_iter_unix_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct bpf_unix_iter_state *iter = seq->private;
	struct sock *sk;

	/* Whenever seq_next() is called, the iter->cur_sk is
	 * done with seq_show(), so advance to the next sk in
	 * the batch.
	 */
	if (iter->cur_sk < iter->end_sk)
		sock_put(iter->batch[iter->cur_sk++]);

	++*pos;

	if (iter->cur_sk < iter->end_sk)
		sk = iter->batch[iter->cur_sk];
	else
		sk = bpf_iter_unix_batch(seq, pos);

	return sk;
}

static int bpf_iter_unix_seq_show(struct seq_file *seq, void *v)
{
	struct bpf_iter_meta meta;
	struct bpf_prog *prog;
	struct sock *sk = v;
	uid_t uid;
	bool slow;
	int ret;

	if (v == SEQ_START_TOKEN)
		return 0;

	slow = lock_sock_fast(sk);

	if (unlikely(sk_unhashed(sk))) {
		ret = SEQ_SKIP;
		goto unlock;
	}

	uid = from_kuid_munged(seq_user_ns(seq), sock_i_uid(sk));
	meta.seq = seq;
	prog = bpf_iter_get_info(&meta, false);
	ret = unix_prog_seq_show(prog, &meta, v, uid);
unlock:
	unlock_sock_fast(sk, slow);
	return ret;
}

static void bpf_iter_unix_seq_stop(struct seq_file *seq, void *v)
{
	struct bpf_unix_iter_state *iter = seq->private;
	struct bpf_iter_meta meta;
	struct bpf_prog *prog;

	if (!v) {
		meta.seq = seq;
		prog = bpf_iter_get_info(&meta, true);
		if (prog)
			(void)unix_prog_seq_show(prog, &meta, v, 0);
	}

	if (iter->cur_sk < iter->end_sk)
		bpf_iter_unix_put_batch(iter);
}

static const struct seq_operations bpf_iter_unix_seq_ops = {
	.start	= bpf_iter_unix_seq_start,
	.next	= bpf_iter_unix_seq_next,
	.stop	= bpf_iter_unix_seq_stop,
	.show	= bpf_iter_unix_seq_show,
};
#endif
#endif

static const struct net_proto_family unix_family_ops = {
	.family = PF_UNIX,
	.create = unix_create,
	.owner	= THIS_MODULE,
};


static int __net_init unix_net_init(struct net *net)
{
	int i;

	net->unx.sysctl_max_dgram_qlen = 10;
	if (unix_sysctl_register(net))
		goto out;

#ifdef CONFIG_PROC_FS
	if (!proc_create_net("unix", 0, net->proc_net, &unix_seq_ops,
			     sizeof(struct seq_net_private)))
		goto err_sysctl;
#endif

	net->unx.table.locks = kvmalloc_array(UNIX_HASH_SIZE,
					      sizeof(spinlock_t), GFP_KERNEL);
	if (!net->unx.table.locks)
		goto err_proc;

	net->unx.table.buckets = kvmalloc_array(UNIX_HASH_SIZE,
						sizeof(struct hlist_head),
						GFP_KERNEL);
	if (!net->unx.table.buckets)
		goto free_locks;

	for (i = 0; i < UNIX_HASH_SIZE; i++) {
		spin_lock_init(&net->unx.table.locks[i]);
		INIT_HLIST_HEAD(&net->unx.table.buckets[i]);
	}

	return 0;

free_locks:
	kvfree(net->unx.table.locks);
err_proc:
#ifdef CONFIG_PROC_FS
	remove_proc_entry("unix", net->proc_net);
err_sysctl:
#endif
	unix_sysctl_unregister(net);
out:
	return -ENOMEM;
}

static void __net_exit unix_net_exit(struct net *net)
{
	kvfree(net->unx.table.buckets);
	kvfree(net->unx.table.locks);
	unix_sysctl_unregister(net);
	remove_proc_entry("unix", net->proc_net);
}

static struct pernet_operations unix_net_ops = {
	.init = unix_net_init,
	.exit = unix_net_exit,
};

#if IS_BUILTIN(CONFIG_UNIX) && defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
DEFINE_BPF_ITER_FUNC(unix, struct bpf_iter_meta *meta,
		     struct unix_sock *unix_sk, uid_t uid)

#define INIT_BATCH_SZ 16

static int bpf_iter_init_unix(void *priv_data, struct bpf_iter_aux_info *aux)
{
	struct bpf_unix_iter_state *iter = priv_data;
	int err;

	err = bpf_iter_init_seq_net(priv_data, aux);
	if (err)
		return err;

	err = bpf_iter_unix_realloc_batch(iter, INIT_BATCH_SZ);
	if (err) {
		bpf_iter_fini_seq_net(priv_data);
		return err;
	}

	return 0;
}

static void bpf_iter_fini_unix(void *priv_data)
{
	struct bpf_unix_iter_state *iter = priv_data;

	bpf_iter_fini_seq_net(priv_data);
	kvfree(iter->batch);
}

static const struct bpf_iter_seq_info unix_seq_info = {
	.seq_ops		= &bpf_iter_unix_seq_ops,
	.init_seq_private	= bpf_iter_init_unix,
	.fini_seq_private	= bpf_iter_fini_unix,
	.seq_priv_size		= sizeof(struct bpf_unix_iter_state),
};

static const struct bpf_func_proto *
bpf_iter_unix_get_func_proto(enum bpf_func_id func_id,
			     const struct bpf_prog *prog)
{
	switch (func_id) {
	case BPF_FUNC_setsockopt:
		return &bpf_sk_setsockopt_proto;
	case BPF_FUNC_getsockopt:
		return &bpf_sk_getsockopt_proto;
	default:
		return NULL;
	}
}

static struct bpf_iter_reg unix_reg_info = {
	.target			= "unix",
	.ctx_arg_info_size	= 1,
	.ctx_arg_info		= {
		{ offsetof(struct bpf_iter__unix, unix_sk),
		  PTR_TO_BTF_ID_OR_NULL },
	},
	.get_func_proto         = bpf_iter_unix_get_func_proto,
	.seq_info		= &unix_seq_info,
};

static void __init bpf_iter_register(void)
{
	unix_reg_info.ctx_arg_info[0].btf_id = btf_sock_ids[BTF_SOCK_TYPE_UNIX];
	if (bpf_iter_reg_target(&unix_reg_info))
		pr_warn("Warning: could not register bpf iterator unix\n");
}
#endif

static int __init af_unix_init(void)
{
	int i, rc = -1;

	BUILD_BUG_ON(sizeof(struct unix_skb_parms) > sizeof_field(struct sk_buff, cb));

	for (i = 0; i < UNIX_HASH_SIZE / 2; i++) {
		spin_lock_init(&bsd_socket_locks[i]);
		INIT_HLIST_HEAD(&bsd_socket_buckets[i]);
	}

	rc = proto_register(&unix_dgram_proto, 1);
	if (rc != 0) {
		pr_crit("%s: Cannot create unix_sock SLAB cache!\n", __func__);
		goto out;
	}

	rc = proto_register(&unix_stream_proto, 1);
	if (rc != 0) {
		pr_crit("%s: Cannot create unix_sock SLAB cache!\n", __func__);
		proto_unregister(&unix_dgram_proto);
		goto out;
	}

	sock_register(&unix_family_ops);
	register_pernet_subsys(&unix_net_ops);
	unix_bpf_build_proto();

#if IS_BUILTIN(CONFIG_UNIX) && defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
	bpf_iter_register();
#endif

out:
	return rc;
}

static void __exit af_unix_exit(void)
{
	sock_unregister(PF_UNIX);
	proto_unregister(&unix_dgram_proto);
	proto_unregister(&unix_stream_proto);
	unregister_pernet_subsys(&unix_net_ops);
}

/* Earlier than device_initcall() so that other drivers invoking
   request_module() don't end up in a loop when modprobe tries
   to use a UNIX socket. But later than subsys_initcall() because
   we depend on stuff initialised there */
fs_initcall(af_unix_init);
module_exit(af_unix_exit);

MODULE_LICENSE("GPL");
MODULE_IMPORT_NS(VFS_internal_I_am_really_a_filesystem_and_am_NOT_a_driver);
MODULE_ALIAS_NETPROTO(PF_UNIX);