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