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/sched/signal.h>
12 #include <linux/types.h>
13 #include <linux/wait.h>
14 #include <linux/audit.h>
15 #include <linux/sched/mm.h>
19 static bool should_merge(struct fsnotify_event *old_fsn,
20 struct fsnotify_event *new_fsn)
22 struct fanotify_event_info *old, *new;
24 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
25 old = FANOTIFY_E(old_fsn);
26 new = FANOTIFY_E(new_fsn);
28 if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
29 old->path.mnt == new->path.mnt &&
30 old->path.dentry == new->path.dentry)
35 /* and the list better be locked by something too! */
36 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
38 struct fsnotify_event *test_event;
40 pr_debug("%s: list=%p event=%p\n", __func__, list, event);
43 * Don't merge a permission event with any other event so that we know
44 * the event structure we have created in fanotify_handle_event() is the
45 * one we should check for permission response.
47 if (fanotify_is_perm_event(event->mask))
50 list_for_each_entry_reverse(test_event, list, list) {
51 if (should_merge(test_event, event)) {
52 test_event->mask |= event->mask;
60 static int fanotify_get_response(struct fsnotify_group *group,
61 struct fanotify_perm_event_info *event,
62 struct fsnotify_iter_info *iter_info)
66 pr_debug("%s: group=%p event=%p\n", __func__, group, event);
68 wait_event(group->fanotify_data.access_waitq, event->response);
70 /* userspace responded, convert to something usable */
71 switch (event->response & ~FAN_AUDIT) {
80 /* Check if the response should be audited */
81 if (event->response & FAN_AUDIT)
82 audit_fanotify(event->response & ~FAN_AUDIT);
86 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
92 static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
93 u32 event_mask, const void *data,
96 __u32 marks_mask = 0, marks_ignored_mask = 0;
97 const struct path *path = data;
98 struct fsnotify_mark *mark;
101 pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
102 __func__, iter_info->report_mask, event_mask, data, data_type);
104 /* if we don't have enough info to send an event to userspace say no */
105 if (data_type != FSNOTIFY_EVENT_PATH)
108 /* sorry, fanotify only gives a damn about files and dirs */
109 if (!d_is_reg(path->dentry) &&
110 !d_can_lookup(path->dentry))
113 fsnotify_foreach_obj_type(type) {
114 if (!fsnotify_iter_should_report_type(iter_info, type))
116 mark = iter_info->marks[type];
118 /* Apply ignore mask regardless of ISDIR and ON_CHILD flags */
119 marks_ignored_mask |= mark->ignored_mask;
122 * If the event is for a child and this mark doesn't care about
123 * events on a child, don't send it!
125 if (event_mask & FS_EVENT_ON_CHILD &&
126 (type != FSNOTIFY_OBJ_TYPE_INODE ||
127 !(mark->mask & FS_EVENT_ON_CHILD)))
130 marks_mask |= mark->mask;
133 if (d_is_dir(path->dentry) &&
134 !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
137 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
144 struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group,
145 struct inode *inode, u32 mask,
146 const struct path *path)
148 struct fanotify_event_info *event = NULL;
149 gfp_t gfp = GFP_KERNEL_ACCOUNT;
152 * For queues with unlimited length lost events are not expected and
153 * can possibly have security implications. Avoid losing events when
154 * memory is short. For the limited size queues, avoid OOM killer in the
155 * target monitoring memcg as it may have security repercussion.
157 if (group->max_events == UINT_MAX)
160 gfp |= __GFP_RETRY_MAYFAIL;
162 /* Whoever is interested in the event, pays for the allocation. */
163 memalloc_use_memcg(group->memcg);
165 if (fanotify_is_perm_event(mask)) {
166 struct fanotify_perm_event_info *pevent;
168 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
171 event = &pevent->fae;
172 pevent->response = 0;
175 event = kmem_cache_alloc(fanotify_event_cachep, gfp);
179 fsnotify_init_event(&event->fse, inode, mask);
180 event->tgid = get_pid(task_tgid(current));
183 path_get(&event->path);
185 event->path.mnt = NULL;
186 event->path.dentry = NULL;
189 memalloc_unuse_memcg();
193 static int fanotify_handle_event(struct fsnotify_group *group,
195 u32 mask, const void *data, int data_type,
196 const unsigned char *file_name, u32 cookie,
197 struct fsnotify_iter_info *iter_info)
200 struct fanotify_event_info *event;
201 struct fsnotify_event *fsn_event;
203 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
204 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
205 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
206 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
207 BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
208 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
209 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
210 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
211 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
212 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
214 if (!fanotify_should_send_event(iter_info, mask, data, data_type))
217 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
220 if (fanotify_is_perm_event(mask)) {
222 * fsnotify_prepare_user_wait() fails if we race with mark
223 * deletion. Just let the operation pass in that case.
225 if (!fsnotify_prepare_user_wait(iter_info))
229 event = fanotify_alloc_event(group, inode, mask, data);
231 if (unlikely(!event)) {
233 * We don't queue overflow events for permission events as
234 * there the access is denied and so no event is in fact lost.
236 if (!fanotify_is_perm_event(mask))
237 fsnotify_queue_overflow(group);
241 fsn_event = &event->fse;
242 ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
244 /* Permission events shouldn't be merged */
245 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
246 /* Our event wasn't used in the end. Free it. */
247 fsnotify_destroy_event(group, fsn_event);
250 } else if (fanotify_is_perm_event(mask)) {
251 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
253 fsnotify_destroy_event(group, fsn_event);
256 if (fanotify_is_perm_event(mask))
257 fsnotify_finish_user_wait(iter_info);
262 static void fanotify_free_group_priv(struct fsnotify_group *group)
264 struct user_struct *user;
266 user = group->fanotify_data.user;
267 atomic_dec(&user->fanotify_listeners);
271 static void fanotify_free_event(struct fsnotify_event *fsn_event)
273 struct fanotify_event_info *event;
275 event = FANOTIFY_E(fsn_event);
276 path_put(&event->path);
277 put_pid(event->tgid);
278 if (fanotify_is_perm_event(fsn_event->mask)) {
279 kmem_cache_free(fanotify_perm_event_cachep,
280 FANOTIFY_PE(fsn_event));
283 kmem_cache_free(fanotify_event_cachep, event);
286 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
288 kmem_cache_free(fanotify_mark_cache, fsn_mark);
291 const struct fsnotify_ops fanotify_fsnotify_ops = {
292 .handle_event = fanotify_handle_event,
293 .free_group_priv = fanotify_free_group_priv,
294 .free_event = fanotify_free_event,
295 .free_mark = fanotify_free_mark,