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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 | #include "internal.h" |
8 | |
9 | static inline void path_get_longterm(struct path *path) |
10 | { |
11 | path_get(path); |
12 | mnt_make_longterm(path->mnt); |
13 | } |
14 | |
15 | static 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 | */ |
25 | void set_fs_root(struct fs_struct *fs, struct path *path) |
26 | { |
27 | struct path old_root; |
28 | |
29 | spin_lock(&fs->lock); |
30 | write_seqcount_begin(&fs->seq); |
31 | old_root = fs->root; |
32 | fs->root = *path; |
33 | path_get_longterm(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 | */ |
44 | void set_fs_pwd(struct fs_struct *fs, struct path *path) |
45 | { |
46 | struct path old_pwd; |
47 | |
48 | spin_lock(&fs->lock); |
49 | write_seqcount_begin(&fs->seq); |
50 | old_pwd = fs->pwd; |
51 | fs->pwd = *path; |
52 | path_get_longterm(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 | |
60 | void chroot_fs_refs(struct path *old_root, struct path *new_root) |
61 | { |
62 | struct task_struct *g, *p; |
63 | struct fs_struct *fs; |
64 | int count = 0; |
65 | |
66 | read_lock(&tasklist_lock); |
67 | do_each_thread(g, p) { |
68 | task_lock(p); |
69 | fs = p->fs; |
70 | if (fs) { |
71 | spin_lock(&fs->lock); |
72 | write_seqcount_begin(&fs->seq); |
73 | if (fs->root.dentry == old_root->dentry |
74 | && fs->root.mnt == old_root->mnt) { |
75 | path_get_longterm(new_root); |
76 | fs->root = *new_root; |
77 | count++; |
78 | } |
79 | if (fs->pwd.dentry == old_root->dentry |
80 | && fs->pwd.mnt == old_root->mnt) { |
81 | path_get_longterm(new_root); |
82 | fs->pwd = *new_root; |
83 | count++; |
84 | } |
85 | write_seqcount_end(&fs->seq); |
86 | spin_unlock(&fs->lock); |
87 | } |
88 | task_unlock(p); |
89 | } while_each_thread(g, p); |
90 | read_unlock(&tasklist_lock); |
91 | while (count--) |
92 | path_put_longterm(old_root); |
93 | } |
94 | |
95 | void free_fs_struct(struct fs_struct *fs) |
96 | { |
97 | path_put_longterm(&fs->root); |
98 | path_put_longterm(&fs->pwd); |
99 | kmem_cache_free(fs_cachep, fs); |
100 | } |
101 | |
102 | void exit_fs(struct task_struct *tsk) |
103 | { |
104 | struct fs_struct *fs = tsk->fs; |
105 | |
106 | if (fs) { |
107 | int kill; |
108 | task_lock(tsk); |
109 | spin_lock(&fs->lock); |
110 | write_seqcount_begin(&fs->seq); |
111 | tsk->fs = NULL; |
112 | kill = !--fs->users; |
113 | write_seqcount_end(&fs->seq); |
114 | spin_unlock(&fs->lock); |
115 | task_unlock(tsk); |
116 | if (kill) |
117 | free_fs_struct(fs); |
118 | } |
119 | } |
120 | |
121 | struct fs_struct *copy_fs_struct(struct fs_struct *old) |
122 | { |
123 | struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); |
124 | /* We don't need to lock fs - think why ;-) */ |
125 | if (fs) { |
126 | fs->users = 1; |
127 | fs->in_exec = 0; |
128 | spin_lock_init(&fs->lock); |
129 | seqcount_init(&fs->seq); |
130 | fs->umask = old->umask; |
131 | |
132 | spin_lock(&old->lock); |
133 | fs->root = old->root; |
134 | path_get_longterm(&fs->root); |
135 | fs->pwd = old->pwd; |
136 | path_get_longterm(&fs->pwd); |
137 | spin_unlock(&old->lock); |
138 | } |
139 | return fs; |
140 | } |
141 | |
142 | int unshare_fs_struct(void) |
143 | { |
144 | struct fs_struct *fs = current->fs; |
145 | struct fs_struct *new_fs = copy_fs_struct(fs); |
146 | int kill; |
147 | |
148 | if (!new_fs) |
149 | return -ENOMEM; |
150 | |
151 | task_lock(current); |
152 | spin_lock(&fs->lock); |
153 | kill = !--fs->users; |
154 | current->fs = new_fs; |
155 | spin_unlock(&fs->lock); |
156 | task_unlock(current); |
157 | |
158 | if (kill) |
159 | free_fs_struct(fs); |
160 | |
161 | return 0; |
162 | } |
163 | EXPORT_SYMBOL_GPL(unshare_fs_struct); |
164 | |
165 | int current_umask(void) |
166 | { |
167 | return current->fs->umask; |
168 | } |
169 | EXPORT_SYMBOL(current_umask); |
170 | |
171 | /* to be mentioned only in INIT_TASK */ |
172 | struct fs_struct init_fs = { |
173 | .users = 1, |
174 | .lock = __SPIN_LOCK_UNLOCKED(init_fs.lock), |
175 | .seq = SEQCNT_ZERO, |
176 | .umask = 0022, |
177 | }; |
178 | |
179 | void daemonize_fs_struct(void) |
180 | { |
181 | struct fs_struct *fs = current->fs; |
182 | |
183 | if (fs) { |
184 | int kill; |
185 | |
186 | task_lock(current); |
187 | |
188 | spin_lock(&init_fs.lock); |
189 | init_fs.users++; |
190 | spin_unlock(&init_fs.lock); |
191 | |
192 | spin_lock(&fs->lock); |
193 | current->fs = &init_fs; |
194 | kill = !--fs->users; |
195 | spin_unlock(&fs->lock); |
196 | |
197 | task_unlock(current); |
198 | if (kill) |
199 | free_fs_struct(fs); |
200 | } |
201 | } |
202 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9