blob: af1b24fa899d0322fc8614960f9bfb13bcdd816e [file] [log] [blame]
Al Viroe149ed22014-11-01 10:57:28 -04001#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
8static struct vfsmount *nsfs_mnt;
9
10static const struct file_operations ns_file_operations = {
11 .llseek = no_llseek,
12};
13
14static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
15{
16 struct inode *inode = dentry->d_inode;
17 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
18
19 return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
20 ns_ops->name, inode->i_ino);
21}
22
23static void ns_prune_dentry(struct dentry *dentry)
24{
25 struct inode *inode = dentry->d_inode;
26 if (inode) {
27 struct ns_common *ns = inode->i_private;
28 atomic_long_set(&ns->stashed, 0);
29 }
30}
31
32const struct dentry_operations ns_dentry_operations =
33{
34 .d_prune = ns_prune_dentry,
35 .d_delete = always_delete_dentry,
36 .d_dname = ns_dname,
37};
38
39static void nsfs_evict(struct inode *inode)
40{
41 struct ns_common *ns = inode->i_private;
42 clear_inode(inode);
43 ns->ops->put(ns);
44}
45
46void *ns_get_path(struct path *path, struct task_struct *task,
47 const struct proc_ns_operations *ns_ops)
48{
49 struct vfsmount *mnt = mntget(nsfs_mnt);
50 struct qstr qname = { .name = "", };
51 struct dentry *dentry;
52 struct inode *inode;
53 struct ns_common *ns;
54 unsigned long d;
55
56again:
57 ns = ns_ops->get(task);
58 if (!ns) {
59 mntput(mnt);
60 return ERR_PTR(-ENOENT);
61 }
62 rcu_read_lock();
63 d = atomic_long_read(&ns->stashed);
64 if (!d)
65 goto slow;
66 dentry = (struct dentry *)d;
67 if (!lockref_get_not_dead(&dentry->d_lockref))
68 goto slow;
69 rcu_read_unlock();
70 ns_ops->put(ns);
71got_it:
72 path->mnt = mnt;
73 path->dentry = dentry;
74 return NULL;
75slow:
76 rcu_read_unlock();
77 inode = new_inode_pseudo(mnt->mnt_sb);
78 if (!inode) {
79 ns_ops->put(ns);
80 mntput(mnt);
81 return ERR_PTR(-ENOMEM);
82 }
83 inode->i_ino = ns->inum;
84 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
85 inode->i_flags |= S_IMMUTABLE;
86 inode->i_mode = S_IFREG | S_IRUGO;
87 inode->i_fop = &ns_file_operations;
88 inode->i_private = ns;
89
90 dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
91 if (!dentry) {
92 iput(inode);
93 mntput(mnt);
94 return ERR_PTR(-ENOMEM);
95 }
96 d_instantiate(dentry, inode);
97 dentry->d_fsdata = (void *)ns_ops;
98 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
99 if (d) {
100 d_delete(dentry); /* make sure ->d_prune() does nothing */
101 dput(dentry);
102 cpu_relax();
103 goto again;
104 }
105 goto got_it;
106}
107
108int ns_get_name(char *buf, size_t size, struct task_struct *task,
109 const struct proc_ns_operations *ns_ops)
110{
111 struct ns_common *ns;
112 int res = -ENOENT;
113 ns = ns_ops->get(task);
114 if (ns) {
115 res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
116 ns_ops->put(ns);
117 }
118 return res;
119}
120
121struct file *proc_ns_fget(int fd)
122{
123 struct file *file;
124
125 file = fget(fd);
126 if (!file)
127 return ERR_PTR(-EBADF);
128
129 if (file->f_op != &ns_file_operations)
130 goto out_invalid;
131
132 return file;
133
134out_invalid:
135 fput(file);
136 return ERR_PTR(-EINVAL);
137}
138
139static const struct super_operations nsfs_ops = {
140 .statfs = simple_statfs,
141 .evict_inode = nsfs_evict,
142};
143static struct dentry *nsfs_mount(struct file_system_type *fs_type,
144 int flags, const char *dev_name, void *data)
145{
146 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
147 &ns_dentry_operations, NSFS_MAGIC);
148}
149static struct file_system_type nsfs = {
150 .name = "nsfs",
151 .mount = nsfs_mount,
152 .kill_sb = kill_anon_super,
153};
154
155void __init nsfs_init(void)
156{
157 nsfs_mnt = kern_mount(&nsfs);
158 if (IS_ERR(nsfs_mnt))
159 panic("can't set nsfs up\n");
160 nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
161}