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, marks_ignored_mask;
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 (!S_ISREG(path->dentry->d_inode->i_mode) &&
108 !S_ISDIR(path->dentry->d_inode->i_mode))
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 (S_ISDIR(path->dentry->d_inode->i_mode) &&
132 (marks_ignored_mask & FS_ISDIR))
133 return false;
134
135 if (event_mask & marks_mask & ~marks_ignored_mask)
136 return true;
137
138 return false;
139 }
140
fanotify_alloc_event(struct inode * inode,u32 mask,struct path * path)141 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
142 struct path *path)
143 {
144 struct fanotify_event_info *event;
145
146 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
147 if (mask & FAN_ALL_PERM_EVENTS) {
148 struct fanotify_perm_event_info *pevent;
149
150 pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
151 GFP_KERNEL);
152 if (!pevent)
153 return NULL;
154 event = &pevent->fae;
155 pevent->response = 0;
156 goto init;
157 }
158 #endif
159 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
160 if (!event)
161 return NULL;
162 init: __maybe_unused
163 fsnotify_init_event(&event->fse, inode, mask);
164 event->tgid = get_pid(task_tgid(current));
165 if (path) {
166 event->path = *path;
167 path_get(&event->path);
168 } else {
169 event->path.mnt = NULL;
170 event->path.dentry = NULL;
171 }
172 return event;
173 }
174
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)175 static int fanotify_handle_event(struct fsnotify_group *group,
176 struct inode *inode,
177 struct fsnotify_mark *inode_mark,
178 struct fsnotify_mark *fanotify_mark,
179 u32 mask, void *data, int data_type,
180 const unsigned char *file_name, u32 cookie)
181 {
182 int ret = 0;
183 struct fanotify_event_info *event;
184 struct fsnotify_event *fsn_event;
185
186 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
187 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
188 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
189 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
190 BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
191 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
192 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
193 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
194 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
195 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
196
197 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
198 data_type))
199 return 0;
200
201 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
202 mask);
203
204 event = fanotify_alloc_event(inode, mask, data);
205 if (unlikely(!event))
206 return -ENOMEM;
207
208 fsn_event = &event->fse;
209 ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
210 if (ret) {
211 /* Permission events shouldn't be merged */
212 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
213 /* Our event wasn't used in the end. Free it. */
214 fsnotify_destroy_event(group, fsn_event);
215
216 return 0;
217 }
218
219 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
220 if (mask & FAN_ALL_PERM_EVENTS) {
221 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
222 fsnotify_destroy_event(group, fsn_event);
223 }
224 #endif
225 return ret;
226 }
227
fanotify_free_group_priv(struct fsnotify_group * group)228 static void fanotify_free_group_priv(struct fsnotify_group *group)
229 {
230 struct user_struct *user;
231
232 user = group->fanotify_data.user;
233 atomic_dec(&user->fanotify_listeners);
234 free_uid(user);
235 }
236
fanotify_free_event(struct fsnotify_event * fsn_event)237 static void fanotify_free_event(struct fsnotify_event *fsn_event)
238 {
239 struct fanotify_event_info *event;
240
241 event = FANOTIFY_E(fsn_event);
242 path_put(&event->path);
243 put_pid(event->tgid);
244 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
245 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
246 kmem_cache_free(fanotify_perm_event_cachep,
247 FANOTIFY_PE(fsn_event));
248 return;
249 }
250 #endif
251 kmem_cache_free(fanotify_event_cachep, event);
252 }
253
254 const struct fsnotify_ops fanotify_fsnotify_ops = {
255 .handle_event = fanotify_handle_event,
256 .free_group_priv = fanotify_free_group_priv,
257 .free_event = fanotify_free_event,
258 };
259