1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/cache.h>
3 #include <linux/sched.h>
4 #include <linux/slab.h>
5 #include <linux/pid_namespace.h>
6 #include "internal.h"
7
8 /*
9 * /proc/thread_self:
10 */
proc_thread_self_get_link(struct dentry * dentry,struct inode * inode,struct delayed_call * done)11 static const char *proc_thread_self_get_link(struct dentry *dentry,
12 struct inode *inode,
13 struct delayed_call *done)
14 {
15 struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
16 pid_t tgid = task_tgid_nr_ns(current, ns);
17 pid_t pid = task_pid_nr_ns(current, ns);
18 char *name;
19
20 /*
21 * Not currently supported. Once we can inherit all of struct pid,
22 * we can allow this.
23 */
24 if (current->flags & PF_IO_WORKER)
25 return ERR_PTR(-EOPNOTSUPP);
26
27 if (!pid)
28 return ERR_PTR(-ENOENT);
29 name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
30 if (unlikely(!name))
31 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
32 sprintf(name, "%u/task/%u", tgid, pid);
33 set_delayed_call(done, kfree_link, name);
34 return name;
35 }
36
37 static const struct inode_operations proc_thread_self_inode_operations = {
38 .get_link = proc_thread_self_get_link,
39 };
40
41 static unsigned thread_self_inum __ro_after_init;
42
proc_setup_thread_self(struct super_block * s)43 int proc_setup_thread_self(struct super_block *s)
44 {
45 struct inode *root_inode = d_inode(s->s_root);
46 struct proc_fs_info *fs_info = proc_sb_info(s);
47 struct dentry *thread_self;
48 int ret = -ENOMEM;
49
50 inode_lock(root_inode);
51 thread_self = d_alloc_name(s->s_root, "thread-self");
52 if (thread_self) {
53 struct inode *inode = new_inode(s);
54 if (inode) {
55 inode->i_ino = thread_self_inum;
56 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
57 inode->i_mode = S_IFLNK | S_IRWXUGO;
58 inode->i_uid = GLOBAL_ROOT_UID;
59 inode->i_gid = GLOBAL_ROOT_GID;
60 inode->i_op = &proc_thread_self_inode_operations;
61 d_add(thread_self, inode);
62 ret = 0;
63 } else {
64 dput(thread_self);
65 }
66 }
67 inode_unlock(root_inode);
68
69 if (ret)
70 pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
71 else
72 fs_info->proc_thread_self = thread_self;
73
74 return ret;
75 }
76
proc_thread_self_init(void)77 void __init proc_thread_self_init(void)
78 {
79 proc_alloc_inum(&thread_self_inum);
80 }
81