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
should_merge(struct fsnotify_event * old_fsn,struct fsnotify_event * new_fsn)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! */
fanotify_merge(struct list_head * list,struct fsnotify_event * event)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
fanotify_get_response(struct fsnotify_group * group,struct fanotify_perm_event_info * event)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
fanotify_should_send_event(struct fsnotify_mark * inode_mark,struct fsnotify_mark * vfsmnt_mark,u32 event_mask,void * data,int data_type)90 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
91 struct fsnotify_mark *vfsmnt_mark,
92 u32 event_mask,
93 void *data, int data_type)
94 {
95 __u32 marks_mask = 0, marks_ignored_mask = 0;
96 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 /*
112 * if the event is for a child and this inode doesn't care about
113 * events on the child, don't send it!
114 */
115 if (inode_mark &&
116 (!(event_mask & FS_EVENT_ON_CHILD) ||
117 (inode_mark->mask & FS_EVENT_ON_CHILD))) {
118 marks_mask |= inode_mark->mask;
119 marks_ignored_mask |= inode_mark->ignored_mask;
120 }
121
122 if (vfsmnt_mark) {
123 marks_mask |= vfsmnt_mark->mask;
124 marks_ignored_mask |= vfsmnt_mark->ignored_mask;
125 }
126
127 if (d_is_dir(path->dentry) &&
128 !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
129 return false;
130
131 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
132 ~marks_ignored_mask)
133 return true;
134
135 return false;
136 }
137
fanotify_alloc_event(struct inode * inode,u32 mask,struct path * path)138 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
139 struct path *path)
140 {
141 struct fanotify_event_info *event;
142
143 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
144 if (mask & FAN_ALL_PERM_EVENTS) {
145 struct fanotify_perm_event_info *pevent;
146
147 pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
148 GFP_KERNEL);
149 if (!pevent)
150 return NULL;
151 event = &pevent->fae;
152 pevent->response = 0;
153 goto init;
154 }
155 #endif
156 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
157 if (!event)
158 return NULL;
159 init: __maybe_unused
160 fsnotify_init_event(&event->fse, inode, mask);
161 event->tgid = get_pid(task_tgid(current));
162 if (path) {
163 event->path = *path;
164 path_get(&event->path);
165 } else {
166 event->path.mnt = NULL;
167 event->path.dentry = NULL;
168 }
169 return event;
170 }
171
fanotify_handle_event(struct fsnotify_group * group,struct inode * inode,struct fsnotify_mark * inode_mark,struct fsnotify_mark * fanotify_mark,u32 mask,void * data,int data_type,const unsigned char * file_name,u32 cookie)172 static int fanotify_handle_event(struct fsnotify_group *group,
173 struct inode *inode,
174 struct fsnotify_mark *inode_mark,
175 struct fsnotify_mark *fanotify_mark,
176 u32 mask, void *data, int data_type,
177 const unsigned char *file_name, u32 cookie)
178 {
179 int ret = 0;
180 struct fanotify_event_info *event;
181 struct fsnotify_event *fsn_event;
182
183 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
184 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
185 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
186 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
187 BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
188 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
189 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
190 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
191 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
192 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
193
194 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
195 data_type))
196 return 0;
197
198 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
199 mask);
200
201 event = fanotify_alloc_event(inode, mask, data);
202 if (unlikely(!event))
203 return -ENOMEM;
204
205 fsn_event = &event->fse;
206 ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
207 if (ret) {
208 /* Permission events shouldn't be merged */
209 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
210 /* Our event wasn't used in the end. Free it. */
211 fsnotify_destroy_event(group, fsn_event);
212
213 return 0;
214 }
215
216 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
217 if (mask & FAN_ALL_PERM_EVENTS) {
218 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
219 fsnotify_destroy_event(group, fsn_event);
220 }
221 #endif
222 return ret;
223 }
224
fanotify_free_group_priv(struct fsnotify_group * group)225 static void fanotify_free_group_priv(struct fsnotify_group *group)
226 {
227 struct user_struct *user;
228
229 user = group->fanotify_data.user;
230 atomic_dec(&user->fanotify_listeners);
231 free_uid(user);
232 }
233
fanotify_free_event(struct fsnotify_event * fsn_event)234 static void fanotify_free_event(struct fsnotify_event *fsn_event)
235 {
236 struct fanotify_event_info *event;
237
238 event = FANOTIFY_E(fsn_event);
239 path_put(&event->path);
240 put_pid(event->tgid);
241 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
242 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
243 kmem_cache_free(fanotify_perm_event_cachep,
244 FANOTIFY_PE(fsn_event));
245 return;
246 }
247 #endif
248 kmem_cache_free(fanotify_event_cachep, event);
249 }
250
251 const struct fsnotify_ops fanotify_fsnotify_ops = {
252 .handle_event = fanotify_handle_event,
253 .free_group_priv = fanotify_free_group_priv,
254 .free_event = fanotify_free_event,
255 };
256