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
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 = d_inode(dentry);
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 = d_inode(dentry);
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}
162