bbc175d4213d5776e65ee9a438cf4e90f8c0f6c2
[sfrench/cifs-2.6.git] / fs / notify / fanotify / fanotify.c
1 #include <linux/fanotify.h>
2 #include <linux/fdtable.h>
3 #include <linux/fsnotify_backend.h>
4 #include <linux/init.h>
5 #include <linux/jiffies.h>
6 #include <linux/kernel.h> /* UINT_MAX */
7 #include <linux/mount.h>
8 #include <linux/sched.h>
9 #include <linux/types.h>
10 #include <linux/wait.h>
11
12 #include "fanotify.h"
13
14 static bool should_merge(struct fsnotify_event *old_fsn,
15                          struct fsnotify_event *new_fsn)
16 {
17         struct fanotify_event_info *old, *new;
18
19         pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
20         old = FANOTIFY_E(old_fsn);
21         new = FANOTIFY_E(new_fsn);
22
23         if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
24             old->path.mnt == new->path.mnt &&
25             old->path.dentry == new->path.dentry)
26                 return true;
27         return false;
28 }
29
30 /* and the list better be locked by something too! */
31 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
32 {
33         struct fsnotify_event *test_event;
34         bool do_merge = false;
35
36         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
37
38 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
39         /*
40          * Don't merge a permission event with any other event so that we know
41          * the event structure we have created in fanotify_handle_event() is the
42          * one we should check for permission response.
43          */
44         if (event->mask & FAN_ALL_PERM_EVENTS)
45                 return 0;
46 #endif
47
48         list_for_each_entry_reverse(test_event, list, list) {
49                 if (should_merge(test_event, event)) {
50                         do_merge = true;
51                         break;
52                 }
53         }
54
55         if (!do_merge)
56                 return 0;
57
58         test_event->mask |= event->mask;
59         return 1;
60 }
61
62 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
63 static int fanotify_get_response(struct fsnotify_group *group,
64                                  struct fanotify_perm_event_info *event)
65 {
66         int ret;
67
68         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
69
70         wait_event(group->fanotify_data.access_waitq, event->response);
71
72         /* userspace responded, convert to something usable */
73         switch (event->response) {
74         case FAN_ALLOW:
75                 ret = 0;
76                 break;
77         case FAN_DENY:
78         default:
79                 ret = -EPERM;
80         }
81         event->response = 0;
82
83         pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
84                  group, event, ret);
85         
86         return ret;
87 }
88 #endif
89
90 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
91                                        struct fsnotify_mark *vfsmnt_mark,
92                                        u32 event_mask,
93                                        const void *data, int data_type)
94 {
95         __u32 marks_mask, marks_ignored_mask;
96         const struct path *path = data;
97
98         pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
99                  " data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
100                  event_mask, data, data_type);
101
102         /* if we don't have enough info to send an event to userspace say no */
103         if (data_type != FSNOTIFY_EVENT_PATH)
104                 return false;
105
106         /* sorry, fanotify only gives a damn about files and dirs */
107         if (!d_is_reg(path->dentry) &&
108             !d_can_lookup(path->dentry))
109                 return false;
110
111         if (inode_mark && vfsmnt_mark) {
112                 marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
113                 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
114         } else if (inode_mark) {
115                 /*
116                  * if the event is for a child and this inode doesn't care about
117                  * events on the child, don't send it!
118                  */
119                 if ((event_mask & FS_EVENT_ON_CHILD) &&
120                     !(inode_mark->mask & FS_EVENT_ON_CHILD))
121                         return false;
122                 marks_mask = inode_mark->mask;
123                 marks_ignored_mask = inode_mark->ignored_mask;
124         } else if (vfsmnt_mark) {
125                 marks_mask = vfsmnt_mark->mask;
126                 marks_ignored_mask = vfsmnt_mark->ignored_mask;
127         } else {
128                 BUG();
129         }
130
131         if (d_is_dir(path->dentry) &&
132             !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
133                 return false;
134
135         if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
136                                  ~marks_ignored_mask)
137                 return true;
138
139         return false;
140 }
141
142 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
143                                                  const struct path *path)
144 {
145         struct fanotify_event_info *event;
146
147 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
148         if (mask & FAN_ALL_PERM_EVENTS) {
149                 struct fanotify_perm_event_info *pevent;
150
151                 pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
152                                           GFP_KERNEL);
153                 if (!pevent)
154                         return NULL;
155                 event = &pevent->fae;
156                 pevent->response = 0;
157                 goto init;
158         }
159 #endif
160         event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
161         if (!event)
162                 return NULL;
163 init: __maybe_unused
164         fsnotify_init_event(&event->fse, inode, mask);
165         event->tgid = get_pid(task_tgid(current));
166         if (path) {
167                 event->path = *path;
168                 path_get(&event->path);
169         } else {
170                 event->path.mnt = NULL;
171                 event->path.dentry = NULL;
172         }
173         return event;
174 }
175
176 static int fanotify_handle_event(struct fsnotify_group *group,
177                                  struct inode *inode,
178                                  struct fsnotify_mark *inode_mark,
179                                  struct fsnotify_mark *fanotify_mark,
180                                  u32 mask, const void *data, int data_type,
181                                  const unsigned char *file_name, u32 cookie)
182 {
183         int ret = 0;
184         struct fanotify_event_info *event;
185         struct fsnotify_event *fsn_event;
186
187         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
188         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
189         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
190         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
191         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
192         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
193         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
194         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
195         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
196         BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
197
198         if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
199                                         data_type))
200                 return 0;
201
202         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
203                  mask);
204
205         event = fanotify_alloc_event(inode, mask, data);
206         if (unlikely(!event))
207                 return -ENOMEM;
208
209         fsn_event = &event->fse;
210         ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
211         if (ret) {
212                 /* Permission events shouldn't be merged */
213                 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
214                 /* Our event wasn't used in the end. Free it. */
215                 fsnotify_destroy_event(group, fsn_event);
216
217                 return 0;
218         }
219
220 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
221         if (mask & FAN_ALL_PERM_EVENTS) {
222                 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
223                 fsnotify_destroy_event(group, fsn_event);
224         }
225 #endif
226         return ret;
227 }
228
229 static void fanotify_free_group_priv(struct fsnotify_group *group)
230 {
231         struct user_struct *user;
232
233         user = group->fanotify_data.user;
234         atomic_dec(&user->fanotify_listeners);
235         free_uid(user);
236 }
237
238 static void fanotify_free_event(struct fsnotify_event *fsn_event)
239 {
240         struct fanotify_event_info *event;
241
242         event = FANOTIFY_E(fsn_event);
243         path_put(&event->path);
244         put_pid(event->tgid);
245 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
246         if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
247                 kmem_cache_free(fanotify_perm_event_cachep,
248                                 FANOTIFY_PE(fsn_event));
249                 return;
250         }
251 #endif
252         kmem_cache_free(fanotify_event_cachep, event);
253 }
254
255 const struct fsnotify_ops fanotify_fsnotify_ops = {
256         .handle_event = fanotify_handle_event,
257         .free_group_priv = fanotify_free_group_priv,
258         .free_event = fanotify_free_event,
259 };