blob: e4905fbf3396978b6d5f77319df6f3613f9d4ed7 [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>
Eric W. Biederman75509fd2015-05-24 12:49:04 -05007#include <linux/seq_file.h>
Al Viroe149ed22014-11-01 10:57:28 -04008
9static struct vfsmount *nsfs_mnt;
10
11static const struct file_operations ns_file_operations = {
12 .llseek = no_llseek,
13};
14
15static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
16{
David Howells75c3cfa2015-03-17 22:26:12 +000017 struct inode *inode = d_inode(dentry);
Al Viroe149ed22014-11-01 10:57:28 -040018 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
24static void ns_prune_dentry(struct dentry *dentry)
25{
David Howells75c3cfa2015-03-17 22:26:12 +000026 struct inode *inode = d_inode(dentry);
Al Viroe149ed22014-11-01 10:57:28 -040027 if (inode) {
28 struct ns_common *ns = inode->i_private;
29 atomic_long_set(&ns->stashed, 0);
30 }
31}
32
33const 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
40static 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
47void *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
57again:
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);
72got_it:
73 path->mnt = mnt;
74 path->dentry = dentry;
75 return NULL;
76slow:
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_fsdata = (void *)ns_ops;
99 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
100 if (d) {
101 d_delete(dentry); /* make sure ->d_prune() does nothing */
102 dput(dentry);
103 cpu_relax();
104 goto again;
105 }
106 goto got_it;
107}
108
109int ns_get_name(char *buf, size_t size, struct task_struct *task,
110 const struct proc_ns_operations *ns_ops)
111{
112 struct ns_common *ns;
113 int res = -ENOENT;
114 ns = ns_ops->get(task);
115 if (ns) {
116 res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
117 ns_ops->put(ns);
118 }
119 return res;
120}
121
122struct file *proc_ns_fget(int fd)
123{
124 struct file *file;
125
126 file = fget(fd);
127 if (!file)
128 return ERR_PTR(-EBADF);
129
130 if (file->f_op != &ns_file_operations)
131 goto out_invalid;
132
133 return file;
134
135out_invalid:
136 fput(file);
137 return ERR_PTR(-EINVAL);
138}
139
Eric W. Biederman75509fd2015-05-24 12:49:04 -0500140static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
141{
142 struct inode *inode = d_inode(dentry);
143 const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
144
145 return seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
146}
147
Al Viroe149ed22014-11-01 10:57:28 -0400148static const struct super_operations nsfs_ops = {
149 .statfs = simple_statfs,
150 .evict_inode = nsfs_evict,
Eric W. Biederman75509fd2015-05-24 12:49:04 -0500151 .show_path = nsfs_show_path,
Al Viroe149ed22014-11-01 10:57:28 -0400152};
153static struct dentry *nsfs_mount(struct file_system_type *fs_type,
154 int flags, const char *dev_name, void *data)
155{
156 return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
157 &ns_dentry_operations, NSFS_MAGIC);
158}
159static struct file_system_type nsfs = {
160 .name = "nsfs",
161 .mount = nsfs_mount,
162 .kill_sb = kill_anon_super,
163};
164
165void __init nsfs_init(void)
166{
167 nsfs_mnt = kern_mount(&nsfs);
168 if (IS_ERR(nsfs_mnt))
169 panic("can't set nsfs up\n");
170 nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
171}