1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/fanotify.h>
3 #include <linux/fdtable.h>
4 #include <linux/fsnotify_backend.h>
5 #include <linux/init.h>
6 #include <linux/jiffies.h>
7 #include <linux/kernel.h> /* UINT_MAX */
8 #include <linux/mount.h>
9 #include <linux/sched.h>
10 #include <linux/sched/user.h>
11 #include <linux/types.h>
12 #include <linux/wait.h>
13
14 #include "fanotify.h"
15
should_merge(struct fsnotify_event * old_fsn,struct fsnotify_event * new_fsn)16 static bool should_merge(struct fsnotify_event *old_fsn,
17 struct fsnotify_event *new_fsn)
18 {
19 struct fanotify_event_info *old, *new;
20
21 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
22 old = FANOTIFY_E(old_fsn);
23 new = FANOTIFY_E(new_fsn);
24
25 if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
26 old->path.mnt == new->path.mnt &&
27 old->path.dentry == new->path.dentry)
28 return true;
29 return false;
30 }
31
32 /* and the list better be locked by something too! */
fanotify_merge(struct list_head * list,struct fsnotify_event * event)33 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
34 {
35 struct fsnotify_event *test_event;
36
37 pr_debug("%s: list=%p event=%p\n", __func__, list, event);
38
39 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
40 /*
41 * Don't merge a permission event with any other event so that we know
42 * the event structure we have created in fanotify_handle_event() is the
43 * one we should check for permission response.
44 */
45 if (event->mask & FAN_ALL_PERM_EVENTS)
46 return 0;
47 #endif
48
49 list_for_each_entry_reverse(test_event, list, list) {
50 if (should_merge(test_event, event)) {
51 test_event->mask |= event->mask;
52 return 1;
53 }
54 }
55
56 return 0;
57 }
58
59 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
fanotify_get_response(struct fsnotify_group * group,struct fanotify_perm_event_info * event,struct fsnotify_iter_info * iter_info)60 static int fanotify_get_response(struct fsnotify_group *group,
61 struct fanotify_perm_event_info *event,
62 struct fsnotify_iter_info *iter_info)
63 {
64 int ret;
65
66 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
67
68 wait_event(group->fanotify_data.access_waitq, event->response);
69
70 /* userspace responded, convert to something usable */
71 switch (event->response) {
72 case FAN_ALLOW:
73 ret = 0;
74 break;
75 case FAN_DENY:
76 default:
77 ret = -EPERM;
78 }
79 event->response = 0;
80
81 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
82 group, event, ret);
83
84 return ret;
85 }
86 #endif
87
fanotify_should_send_event(struct fsnotify_mark * inode_mark,struct fsnotify_mark * vfsmnt_mark,u32 event_mask,const void * data,int data_type)88 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
89 struct fsnotify_mark *vfsmnt_mark,
90 u32 event_mask,
91 const void *data, int data_type)
92 {
93 __u32 marks_mask = 0, marks_ignored_mask = 0;
94 const struct path *path = data;
95
96 pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
97 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
98 event_mask, data, data_type);
99
100 /* if we don't have enough info to send an event to userspace say no */
101 if (data_type != FSNOTIFY_EVENT_PATH)
102 return false;
103
104 /* sorry, fanotify only gives a damn about files and dirs */
105 if (!d_is_reg(path->dentry) &&
106 !d_can_lookup(path->dentry))
107 return false;
108
109 /*
110 * if the event is for a child and this inode doesn't care about
111 * events on the child, don't send it!
112 */
113 if (inode_mark &&
114 (!(event_mask & FS_EVENT_ON_CHILD) ||
115 (inode_mark->mask & FS_EVENT_ON_CHILD))) {
116 marks_mask |= inode_mark->mask;
117 marks_ignored_mask |= inode_mark->ignored_mask;
118 }
119
120 if (vfsmnt_mark) {
121 marks_mask |= vfsmnt_mark->mask;
122 marks_ignored_mask |= vfsmnt_mark->ignored_mask;
123 }
124
125 if (d_is_dir(path->dentry) &&
126 !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
127 return false;
128
129 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
130 ~marks_ignored_mask)
131 return true;
132
133 return false;
134 }
135
fanotify_alloc_event(struct inode * inode,u32 mask,const struct path * path)136 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
137 const struct path *path)
138 {
139 struct fanotify_event_info *event;
140
141 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
142 if (mask & FAN_ALL_PERM_EVENTS) {
143 struct fanotify_perm_event_info *pevent;
144
145 pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
146 GFP_KERNEL);
147 if (!pevent)
148 return NULL;
149 event = &pevent->fae;
150 pevent->response = 0;
151 goto init;
152 }
153 #endif
154 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
155 if (!event)
156 return NULL;
157 init: __maybe_unused
158 fsnotify_init_event(&event->fse, inode, mask);
159 event->tgid = get_pid(task_tgid(current));
160 if (path) {
161 event->path = *path;
162 path_get(&event->path);
163 } else {
164 event->path.mnt = NULL;
165 event->path.dentry = NULL;
166 }
167 return event;
168 }
169
fanotify_handle_event(struct fsnotify_group * group,struct inode * inode,struct fsnotify_mark * inode_mark,struct fsnotify_mark * fanotify_mark,u32 mask,const void * data,int data_type,const unsigned char * file_name,u32 cookie,struct fsnotify_iter_info * iter_info)170 static int fanotify_handle_event(struct fsnotify_group *group,
171 struct inode *inode,
172 struct fsnotify_mark *inode_mark,
173 struct fsnotify_mark *fanotify_mark,
174 u32 mask, const void *data, int data_type,
175 const unsigned char *file_name, u32 cookie,
176 struct fsnotify_iter_info *iter_info)
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 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
201 if (mask & FAN_ALL_PERM_EVENTS) {
202 /*
203 * fsnotify_prepare_user_wait() fails if we race with mark
204 * deletion. Just let the operation pass in that case.
205 */
206 if (!fsnotify_prepare_user_wait(iter_info))
207 return 0;
208 }
209 #endif
210
211 event = fanotify_alloc_event(inode, mask, data);
212 ret = -ENOMEM;
213 if (unlikely(!event))
214 goto finish;
215
216 fsn_event = &event->fse;
217 ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
218 if (ret) {
219 /* Permission events shouldn't be merged */
220 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
221 /* Our event wasn't used in the end. Free it. */
222 fsnotify_destroy_event(group, fsn_event);
223
224 ret = 0;
225 goto finish;
226 }
227
228 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
229 if (mask & FAN_ALL_PERM_EVENTS) {
230 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
231 iter_info);
232 fsnotify_destroy_event(group, fsn_event);
233 }
234 finish:
235 if (mask & FAN_ALL_PERM_EVENTS)
236 fsnotify_finish_user_wait(iter_info);
237 #else
238 finish:
239 #endif
240 return ret;
241 }
242
fanotify_free_group_priv(struct fsnotify_group * group)243 static void fanotify_free_group_priv(struct fsnotify_group *group)
244 {
245 struct user_struct *user;
246
247 user = group->fanotify_data.user;
248 atomic_dec(&user->fanotify_listeners);
249 free_uid(user);
250 }
251
fanotify_free_event(struct fsnotify_event * fsn_event)252 static void fanotify_free_event(struct fsnotify_event *fsn_event)
253 {
254 struct fanotify_event_info *event;
255
256 event = FANOTIFY_E(fsn_event);
257 path_put(&event->path);
258 put_pid(event->tgid);
259 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
260 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
261 kmem_cache_free(fanotify_perm_event_cachep,
262 FANOTIFY_PE(fsn_event));
263 return;
264 }
265 #endif
266 kmem_cache_free(fanotify_event_cachep, event);
267 }
268
fanotify_free_mark(struct fsnotify_mark * fsn_mark)269 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
270 {
271 kmem_cache_free(fanotify_mark_cache, fsn_mark);
272 }
273
274 const struct fsnotify_ops fanotify_fsnotify_ops = {
275 .handle_event = fanotify_handle_event,
276 .free_group_priv = fanotify_free_group_priv,
277 .free_event = fanotify_free_event,
278 .free_mark = fanotify_free_mark,
279 };
280