Merge tag 'amd-drm-fixes-5.9-2020-08-20' of git://people.freedesktop.org/~agd5f/linux...
[platform/kernel/linux-starfive.git] / fs / fs_struct.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/export.h>
3 #include <linux/sched/signal.h>
4 #include <linux/sched/task.h>
5 #include <linux/fs.h>
6 #include <linux/path.h>
7 #include <linux/slab.h>
8 #include <linux/fs_struct.h>
9 #include "internal.h"
10
11 /*
12  * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
13  * It can block.
14  */
15 void set_fs_root(struct fs_struct *fs, const struct path *path)
16 {
17         struct path old_root;
18
19         path_get(path);
20         spin_lock(&fs->lock);
21         write_seqcount_begin(&fs->seq);
22         old_root = fs->root;
23         fs->root = *path;
24         write_seqcount_end(&fs->seq);
25         spin_unlock(&fs->lock);
26         if (old_root.dentry)
27                 path_put(&old_root);
28 }
29
30 /*
31  * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
32  * It can block.
33  */
34 void set_fs_pwd(struct fs_struct *fs, const struct path *path)
35 {
36         struct path old_pwd;
37
38         path_get(path);
39         spin_lock(&fs->lock);
40         write_seqcount_begin(&fs->seq);
41         old_pwd = fs->pwd;
42         fs->pwd = *path;
43         write_seqcount_end(&fs->seq);
44         spin_unlock(&fs->lock);
45
46         if (old_pwd.dentry)
47                 path_put(&old_pwd);
48 }
49
50 static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
51 {
52         if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
53                 return 0;
54         *p = *new;
55         return 1;
56 }
57
58 void chroot_fs_refs(const struct path *old_root, const struct path *new_root)
59 {
60         struct task_struct *g, *p;
61         struct fs_struct *fs;
62         int count = 0;
63
64         read_lock(&tasklist_lock);
65         do_each_thread(g, p) {
66                 task_lock(p);
67                 fs = p->fs;
68                 if (fs) {
69                         int hits = 0;
70                         spin_lock(&fs->lock);
71                         write_seqcount_begin(&fs->seq);
72                         hits += replace_path(&fs->root, old_root, new_root);
73                         hits += replace_path(&fs->pwd, old_root, new_root);
74                         write_seqcount_end(&fs->seq);
75                         while (hits--) {
76                                 count++;
77                                 path_get(new_root);
78                         }
79                         spin_unlock(&fs->lock);
80                 }
81                 task_unlock(p);
82         } while_each_thread(g, p);
83         read_unlock(&tasklist_lock);
84         while (count--)
85                 path_put(old_root);
86 }
87
88 void free_fs_struct(struct fs_struct *fs)
89 {
90         path_put(&fs->root);
91         path_put(&fs->pwd);
92         kmem_cache_free(fs_cachep, fs);
93 }
94
95 void exit_fs(struct task_struct *tsk)
96 {
97         struct fs_struct *fs = tsk->fs;
98
99         if (fs) {
100                 int kill;
101                 task_lock(tsk);
102                 spin_lock(&fs->lock);
103                 tsk->fs = NULL;
104                 kill = !--fs->users;
105                 spin_unlock(&fs->lock);
106                 task_unlock(tsk);
107                 if (kill)
108                         free_fs_struct(fs);
109         }
110 }
111
112 struct fs_struct *copy_fs_struct(struct fs_struct *old)
113 {
114         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
115         /* We don't need to lock fs - think why ;-) */
116         if (fs) {
117                 fs->users = 1;
118                 fs->in_exec = 0;
119                 spin_lock_init(&fs->lock);
120                 seqcount_spinlock_init(&fs->seq, &fs->lock);
121                 fs->umask = old->umask;
122
123                 spin_lock(&old->lock);
124                 fs->root = old->root;
125                 path_get(&fs->root);
126                 fs->pwd = old->pwd;
127                 path_get(&fs->pwd);
128                 spin_unlock(&old->lock);
129         }
130         return fs;
131 }
132
133 int unshare_fs_struct(void)
134 {
135         struct fs_struct *fs = current->fs;
136         struct fs_struct *new_fs = copy_fs_struct(fs);
137         int kill;
138
139         if (!new_fs)
140                 return -ENOMEM;
141
142         task_lock(current);
143         spin_lock(&fs->lock);
144         kill = !--fs->users;
145         current->fs = new_fs;
146         spin_unlock(&fs->lock);
147         task_unlock(current);
148
149         if (kill)
150                 free_fs_struct(fs);
151
152         return 0;
153 }
154 EXPORT_SYMBOL_GPL(unshare_fs_struct);
155
156 int current_umask(void)
157 {
158         return current->fs->umask;
159 }
160 EXPORT_SYMBOL(current_umask);
161
162 /* to be mentioned only in INIT_TASK */
163 struct fs_struct init_fs = {
164         .users          = 1,
165         .lock           = __SPIN_LOCK_UNLOCKED(init_fs.lock),
166         .seq            = SEQCNT_SPINLOCK_ZERO(init_fs.seq, &init_fs.lock),
167         .umask          = 0022,
168 };