1#include <linux/module.h>
2#include <linux/sched.h>
3#include <linux/fs.h>
4#include <linux/path.h>
5#include <linux/slab.h>
6#include <linux/fs_struct.h>
7
8/*
9 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
10 * It can block.
11 */
12void set_fs_root(struct fs_struct *fs, struct path *path)
13{
14	struct path old_root;
15
16	spin_lock(&fs->lock);
17	old_root = fs->root;
18	fs->root = *path;
19	path_get(path);
20	spin_unlock(&fs->lock);
21	if (old_root.dentry)
22		path_put(&old_root);
23}
24
25/*
26 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
27 * It can block.
28 */
29void set_fs_pwd(struct fs_struct *fs, struct path *path)
30{
31	struct path old_pwd;
32
33	spin_lock(&fs->lock);
34	old_pwd = fs->pwd;
35	fs->pwd = *path;
36	path_get(path);
37	spin_unlock(&fs->lock);
38
39	if (old_pwd.dentry)
40		path_put(&old_pwd);
41}
42
43void chroot_fs_refs(struct path *old_root, struct path *new_root)
44{
45	struct task_struct *g, *p;
46	struct fs_struct *fs;
47	int count = 0;
48
49	read_lock(&tasklist_lock);
50	do_each_thread(g, p) {
51		task_lock(p);
52		fs = p->fs;
53		if (fs) {
54			spin_lock(&fs->lock);
55			if (fs->root.dentry == old_root->dentry
56			    && fs->root.mnt == old_root->mnt) {
57				path_get(new_root);
58				fs->root = *new_root;
59				count++;
60			}
61			if (fs->pwd.dentry == old_root->dentry
62			    && fs->pwd.mnt == old_root->mnt) {
63				path_get(new_root);
64				fs->pwd = *new_root;
65				count++;
66			}
67			spin_unlock(&fs->lock);
68		}
69		task_unlock(p);
70	} while_each_thread(g, p);
71	read_unlock(&tasklist_lock);
72	while (count--)
73		path_put(old_root);
74}
75
76void free_fs_struct(struct fs_struct *fs)
77{
78	path_put(&fs->root);
79	path_put(&fs->pwd);
80	kmem_cache_free(fs_cachep, fs);
81}
82
83void exit_fs(struct task_struct *tsk)
84{
85	struct fs_struct *fs = tsk->fs;
86
87	if (fs) {
88		int kill;
89		task_lock(tsk);
90		spin_lock(&fs->lock);
91		tsk->fs = NULL;
92		kill = !--fs->users;
93		spin_unlock(&fs->lock);
94		task_unlock(tsk);
95		if (kill)
96			free_fs_struct(fs);
97	}
98}
99
100struct fs_struct *copy_fs_struct(struct fs_struct *old)
101{
102	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
103	/* We don't need to lock fs - think why ;-) */
104	if (fs) {
105		fs->users = 1;
106		fs->in_exec = 0;
107		spin_lock_init(&fs->lock);
108		fs->umask = old->umask;
109		get_fs_root_and_pwd(old, &fs->root, &fs->pwd);
110	}
111	return fs;
112}
113
114int unshare_fs_struct(void)
115{
116	struct fs_struct *fs = current->fs;
117	struct fs_struct *new_fs = copy_fs_struct(fs);
118	int kill;
119
120	if (!new_fs)
121		return -ENOMEM;
122
123	task_lock(current);
124	spin_lock(&fs->lock);
125	kill = !--fs->users;
126	current->fs = new_fs;
127	spin_unlock(&fs->lock);
128	task_unlock(current);
129
130	if (kill)
131		free_fs_struct(fs);
132
133	return 0;
134}
135EXPORT_SYMBOL_GPL(unshare_fs_struct);
136
137int current_umask(void)
138{
139	return current->fs->umask;
140}
141EXPORT_SYMBOL(current_umask);
142
143/* to be mentioned only in INIT_TASK */
144struct fs_struct init_fs = {
145	.users		= 1,
146	.lock		= __SPIN_LOCK_UNLOCKED(init_fs.lock),
147	.umask		= 0022,
148};
149
150void daemonize_fs_struct(void)
151{
152	struct fs_struct *fs = current->fs;
153
154	if (fs) {
155		int kill;
156
157		task_lock(current);
158
159		spin_lock(&init_fs.lock);
160		init_fs.users++;
161		spin_unlock(&init_fs.lock);
162
163		spin_lock(&fs->lock);
164		current->fs = &init_fs;
165		kill = !--fs->users;
166		spin_unlock(&fs->lock);
167
168		task_unlock(current);
169		if (kill)
170			free_fs_struct(fs);
171	}
172}
173