Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#include <linux/export.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#include "internal.h"
8
9static inline void path_get_longterm(struct path *path)
10{
11 path_get(path);
12 mnt_make_longterm(path->mnt);
13}
14
15static inline void path_put_longterm(struct path *path)
16{
17 mnt_make_shortterm(path->mnt);
18 path_put(path);
19}
20
21/*
22 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
23 * It can block.
24 */
25void set_fs_root(struct fs_struct *fs, struct path *path)
26{
27 struct path old_root;
28
29 path_get_longterm(path);
30 spin_lock(&fs->lock);
31 write_seqcount_begin(&fs->seq);
32 old_root = fs->root;
33 fs->root = *path;
34 write_seqcount_end(&fs->seq);
35 spin_unlock(&fs->lock);
36 if (old_root.dentry)
37 path_put_longterm(&old_root);
38}
39
40/*
41 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
42 * It can block.
43 */
44void set_fs_pwd(struct fs_struct *fs, struct path *path)
45{
46 struct path old_pwd;
47
48 path_get_longterm(path);
49 spin_lock(&fs->lock);
50 write_seqcount_begin(&fs->seq);
51 old_pwd = fs->pwd;
52 fs->pwd = *path;
53 write_seqcount_end(&fs->seq);
54 spin_unlock(&fs->lock);
55
56 if (old_pwd.dentry)
57 path_put_longterm(&old_pwd);
58}
59
60static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
61{
62 if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
63 return 0;
64 *p = *new;
65 return 1;
66}
67
68void chroot_fs_refs(struct path *old_root, struct path *new_root)
69{
70 struct task_struct *g, *p;
71 struct fs_struct *fs;
72 int count = 0;
73
74 read_lock(&tasklist_lock);
75 do_each_thread(g, p) {
76 task_lock(p);
77 fs = p->fs;
78 if (fs) {
79 int hits = 0;
80 spin_lock(&fs->lock);
81 write_seqcount_begin(&fs->seq);
82 hits += replace_path(&fs->root, old_root, new_root);
83 hits += replace_path(&fs->pwd, old_root, new_root);
84 write_seqcount_end(&fs->seq);
85 while (hits--) {
86 count++;
87 path_get_longterm(new_root);
88 }
89 spin_unlock(&fs->lock);
90 }
91 task_unlock(p);
92 } while_each_thread(g, p);
93 read_unlock(&tasklist_lock);
94 while (count--)
95 path_put_longterm(old_root);
96}
97
98void free_fs_struct(struct fs_struct *fs)
99{
100 path_put_longterm(&fs->root);
101 path_put_longterm(&fs->pwd);
102 kmem_cache_free(fs_cachep, fs);
103}
104
105void exit_fs(struct task_struct *tsk)
106{
107 struct fs_struct *fs = tsk->fs;
108
109 if (fs) {
110 int kill;
111 task_lock(tsk);
112 spin_lock(&fs->lock);
113 tsk->fs = NULL;
114 kill = !--fs->users;
115 spin_unlock(&fs->lock);
116 task_unlock(tsk);
117 if (kill)
118 free_fs_struct(fs);
119 }
120}
121
122struct fs_struct *copy_fs_struct(struct fs_struct *old)
123{
124 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
125 /* We don't need to lock fs - think why ;-) */
126 if (fs) {
127 fs->users = 1;
128 fs->in_exec = 0;
129 spin_lock_init(&fs->lock);
130 seqcount_init(&fs->seq);
131 fs->umask = old->umask;
132
133 spin_lock(&old->lock);
134 fs->root = old->root;
135 path_get_longterm(&fs->root);
136 fs->pwd = old->pwd;
137 path_get_longterm(&fs->pwd);
138 spin_unlock(&old->lock);
139 }
140 return fs;
141}
142
143int unshare_fs_struct(void)
144{
145 struct fs_struct *fs = current->fs;
146 struct fs_struct *new_fs = copy_fs_struct(fs);
147 int kill;
148
149 if (!new_fs)
150 return -ENOMEM;
151
152 task_lock(current);
153 spin_lock(&fs->lock);
154 kill = !--fs->users;
155 current->fs = new_fs;
156 spin_unlock(&fs->lock);
157 task_unlock(current);
158
159 if (kill)
160 free_fs_struct(fs);
161
162 return 0;
163}
164EXPORT_SYMBOL_GPL(unshare_fs_struct);
165
166int current_umask(void)
167{
168 return current->fs->umask;
169}
170EXPORT_SYMBOL(current_umask);
171
172/* to be mentioned only in INIT_TASK */
173struct fs_struct init_fs = {
174 .users = 1,
175 .lock = __SPIN_LOCK_UNLOCKED(init_fs.lock),
176 .seq = SEQCNT_ZERO,
177 .umask = 0022,
178};
179
180void daemonize_fs_struct(void)
181{
182 struct fs_struct *fs = current->fs;
183
184 if (fs) {
185 int kill;
186
187 task_lock(current);
188
189 spin_lock(&init_fs.lock);
190 init_fs.users++;
191 spin_unlock(&init_fs.lock);
192
193 spin_lock(&fs->lock);
194 current->fs = &init_fs;
195 kill = !--fs->users;
196 spin_unlock(&fs->lock);
197
198 task_unlock(current);
199 if (kill)
200 free_fs_struct(fs);
201 }
202}