1 #include <linux/mount.h>
2 #include <linux/file.h>
3 #include <linux/fs.h>
4 #include <linux/proc_ns.h>
5 #include <linux/magic.h>
6 #include <linux/ktime.h>
7 #include <linux/seq_file.h>
8
9 static struct vfsmount *nsfs_mnt;
10
11 static const struct file_operations ns_file_operations = {
12 .llseek = no_llseek,
13 };
14
ns_dname(struct dentry * dentry,char * buffer,int buflen)15 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
16 {
17 struct inode *inode = d_inode(dentry);
18 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
19
20 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
21 ns_ops->name, inode->i_ino);
22 }
23
ns_prune_dentry(struct dentry * dentry)24 static void ns_prune_dentry(struct dentry *dentry)
25 {
26 struct inode *inode = d_inode(dentry);
27 if (inode) {
28 struct ns_common *ns = inode->i_private;
29 atomic_long_set(&ns->stashed, 0);
30 }
31 }
32
33 const struct dentry_operations ns_dentry_operations =
34 {
35 .d_prune = ns_prune_dentry,
36 .d_delete = always_delete_dentry,
37 .d_dname = ns_dname,
38 };
39
nsfs_evict(struct inode * inode)40 static void nsfs_evict(struct inode *inode)
41 {
42 struct ns_common *ns = inode->i_private;
43 clear_inode(inode);
44 ns->ops->put(ns);
45 }
46
ns_get_path(struct path * path,struct task_struct * task,const struct proc_ns_operations * ns_ops)47 void *ns_get_path(struct path *path, struct task_struct *task,
48 const struct proc_ns_operations *ns_ops)
49 {
50 struct vfsmount *mnt = mntget(nsfs_mnt);
51 struct qstr qname = { .name = "", };
52 struct dentry *dentry;
53 struct inode *inode;
54 struct ns_common *ns;
55 unsigned long d;
56
57 again:
58 ns = ns_ops->get(task);
59 if (!ns) {
60 mntput(mnt);
61 return ERR_PTR(-ENOENT);
62 }
63 rcu_read_lock();
64 d = atomic_long_read(&ns->stashed);
65 if (!d)
66 goto slow;
67 dentry = (struct dentry *)d;
68 if (!lockref_get_not_dead(&dentry->d_lockref))
69 goto slow;
70 rcu_read_unlock();
71 ns_ops->put(ns);
72 got_it:
73 path->mnt = mnt;
74 path->dentry = dentry;
75 return NULL;
76 slow:
77 rcu_read_unlock();
78 inode = new_inode_pseudo(mnt->mnt_sb);
79 if (!inode) {
80 ns_ops->put(ns);
81 mntput(mnt);
82 return ERR_PTR(-ENOMEM);
83 }
84 inode->i_ino = ns->inum;
85 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
86 inode->i_flags |= S_IMMUTABLE;
87 inode->i_mode = S_IFREG | S_IRUGO;
88 inode->i_fop = &ns_file_operations;
89 inode->i_private = ns;
90
91 dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
92 if (!dentry) {
93 iput(inode);
94 mntput(mnt);
95 return ERR_PTR(-ENOMEM);
96 }
97 d_instantiate(dentry, inode);
98 dentry->d_flags |= DCACHE_RCUACCESS;
99 dentry->d_fsdata = (void *)ns_ops;
100 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
101 if (d) {
102 d_delete(dentry); /* make sure ->d_prune() does nothing */
103 dput(dentry);
104 cpu_relax();
105 goto again;
106 }
107 goto got_it;
108 }
109
ns_get_name(char * buf,size_t size,struct task_struct * task,const struct proc_ns_operations * ns_ops)110 int ns_get_name(char *buf, size_t size, struct task_struct *task,
111 const struct proc_ns_operations *ns_ops)
112 {
113 struct ns_common *ns;
114 int res = -ENOENT;
115 ns = ns_ops->get(task);
116 if (ns) {
117 res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
118 ns_ops->put(ns);
119 }
120 return res;
121 }
122
proc_ns_fget(int fd)123 struct file *proc_ns_fget(int fd)
124 {
125 struct file *file;
126
127 file = fget(fd);
128 if (!file)
129 return ERR_PTR(-EBADF);
130
131 if (file->f_op != &ns_file_operations)
132 goto out_invalid;
133
134 return file;
135
136 out_invalid:
137 fput(file);
138 return ERR_PTR(-EINVAL);
139 }
140
nsfs_show_path(struct seq_file * seq,struct dentry * dentry)141 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
142 {
143 struct inode *inode = d_inode(dentry);
144 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
145
146 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
147 return 0;
148 }
149
150 static const struct super_operations nsfs_ops = {
151 .statfs = simple_statfs,
152 .evict_inode = nsfs_evict,
153 .show_path = nsfs_show_path,
154 };
nsfs_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)155 static struct dentry *nsfs_mount(struct file_system_type *fs_type,
156 int flags, const char *dev_name, void *data)
157 {
158 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
159 &ns_dentry_operations, NSFS_MAGIC);
160 }
161 static struct file_system_type nsfs = {
162 .name = "nsfs",
163 .mount = nsfs_mount,
164 .kill_sb = kill_anon_super,
165 };
166
nsfs_init(void)167 void __init nsfs_init(void)
168 {
169 nsfs_mnt = kern_mount(&nsfs);
170 if (IS_ERR(nsfs_mnt))
171 panic("can't set nsfs up\n");
172 nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
173 }
174