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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 | */ | |
12 | void set_fs_root(struct fs_struct *fs, struct path *path) | |
13 | { | |
14 | struct path old_root; | |
15 | ||
16 | write_lock(&fs->lock); | |
17 | old_root = fs->root; | |
18 | fs->root = *path; | |
19 | path_get(path); | |
20 | write_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 | */ | |
29 | void set_fs_pwd(struct fs_struct *fs, struct path *path) | |
30 | { | |
31 | struct path old_pwd; | |
32 | ||
33 | write_lock(&fs->lock); | |
34 | old_pwd = fs->pwd; | |
35 | fs->pwd = *path; | |
36 | path_get(path); | |
37 | write_unlock(&fs->lock); | |
38 | ||
39 | if (old_pwd.dentry) | |
40 | path_put(&old_pwd); | |
41 | } | |
42 | ||
43 | void 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 | write_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 | write_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 | ||
76 | void 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 | ||
83 | void 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 | write_lock(&fs->lock); | |
91 | tsk->fs = NULL; | |
92 | kill = !--fs->users; | |
93 | write_unlock(&fs->lock); | |
94 | task_unlock(tsk); | |
95 | if (kill) | |
96 | free_fs_struct(fs); | |
97 | } | |
98 | } | |
99 | ||
100 | struct 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 | rwlock_init(&fs->lock); | |
108 | fs->umask = old->umask; | |
109 | read_lock(&old->lock); | |
110 | fs->root = old->root; | |
111 | path_get(&old->root); | |
112 | fs->pwd = old->pwd; | |
113 | path_get(&old->pwd); | |
114 | read_unlock(&old->lock); | |
115 | } | |
116 | return fs; | |
117 | } | |
118 | ||
119 | int unshare_fs_struct(void) | |
120 | { | |
121 | struct fs_struct *fs = current->fs; | |
122 | struct fs_struct *new_fs = copy_fs_struct(fs); | |
123 | int kill; | |
124 | ||
125 | if (!new_fs) | |
126 | return -ENOMEM; | |
127 | ||
128 | task_lock(current); | |
129 | write_lock(&fs->lock); | |
130 | kill = !--fs->users; | |
131 | current->fs = new_fs; | |
132 | write_unlock(&fs->lock); | |
133 | task_unlock(current); | |
134 | ||
135 | if (kill) | |
136 | free_fs_struct(fs); | |
137 | ||
138 | return 0; | |
139 | } | |
140 | EXPORT_SYMBOL_GPL(unshare_fs_struct); | |
141 | ||
142 | int current_umask(void) | |
143 | { | |
144 | return current->fs->umask; | |
145 | } | |
146 | EXPORT_SYMBOL(current_umask); | |
147 | ||
148 | /* to be mentioned only in INIT_TASK */ | |
149 | struct fs_struct init_fs = { | |
150 | .users = 1, | |
151 | .lock = __RW_LOCK_UNLOCKED(init_fs.lock), | |
152 | .umask = 0022, | |
153 | }; | |
154 | ||
155 | void daemonize_fs_struct(void) | |
156 | { | |
157 | struct fs_struct *fs = current->fs; | |
158 | ||
159 | if (fs) { | |
160 | int kill; | |
161 | ||
162 | task_lock(current); | |
163 | ||
164 | write_lock(&init_fs.lock); | |
165 | init_fs.users++; | |
166 | write_unlock(&init_fs.lock); | |
167 | ||
168 | write_lock(&fs->lock); | |
169 | current->fs = &init_fs; | |
170 | kill = !--fs->users; | |
171 | write_unlock(&fs->lock); | |
172 | ||
173 | task_unlock(current); | |
174 | if (kill) | |
175 | free_fs_struct(fs); | |
176 | } | |
177 | } |