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 static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new) 13 { 14 pr_debug("%s: old=%p new=%p\n", __func__, old, new); 15 16 if (old->to_tell == new->to_tell && 17 old->data_type == new->data_type && 18 old->tgid == new->tgid) { 19 switch (old->data_type) { 20 case (FSNOTIFY_EVENT_PATH): 21 if ((old->path.mnt == new->path.mnt) && 22 (old->path.dentry == new->path.dentry)) 23 return true; 24 case (FSNOTIFY_EVENT_NONE): 25 return true; 26 default: 27 BUG(); 28 }; 29 } 30 return false; 31 } 32 33 /* and the list better be locked by something too! */ 34 static struct fsnotify_event *fanotify_merge(struct list_head *list, 35 struct fsnotify_event *event) 36 { 37 struct fsnotify_event_holder *test_holder; 38 struct fsnotify_event *test_event = NULL; 39 struct fsnotify_event *new_event; 40 41 pr_debug("%s: list=%p event=%p\n", __func__, list, event); 42 43 44 list_for_each_entry_reverse(test_holder, list, event_list) { 45 if (should_merge(test_holder->event, event)) { 46 test_event = test_holder->event; 47 break; 48 } 49 } 50 51 if (!test_event) 52 return NULL; 53 54 fsnotify_get_event(test_event); 55 56 /* if they are exactly the same we are done */ 57 if (test_event->mask == event->mask) 58 return test_event; 59 60 /* 61 * if the refcnt == 2 this is the only queue 62 * for this event and so we can update the mask 63 * in place. 64 */ 65 if (atomic_read(&test_event->refcnt) == 2) { 66 test_event->mask |= event->mask; 67 return test_event; 68 } 69 70 new_event = fsnotify_clone_event(test_event); 71 72 /* done with test_event */ 73 fsnotify_put_event(test_event); 74 75 /* couldn't allocate memory, merge was not possible */ 76 if (unlikely(!new_event)) 77 return ERR_PTR(-ENOMEM); 78 79 /* build new event and replace it on the list */ 80 new_event->mask = (test_event->mask | event->mask); 81 fsnotify_replace_event(test_holder, new_event); 82 83 /* we hold a reference on new_event from clone_event */ 84 return new_event; 85 } 86 87 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 88 static int fanotify_get_response_from_access(struct fsnotify_group *group, 89 struct fsnotify_event *event) 90 { 91 int ret; 92 93 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 94 95 wait_event(group->fanotify_data.access_waitq, event->response || 96 atomic_read(&group->fanotify_data.bypass_perm)); 97 98 if (!event->response) /* bypass_perm set */ 99 return 0; 100 101 /* userspace responded, convert to something usable */ 102 spin_lock(&event->lock); 103 switch (event->response) { 104 case FAN_ALLOW: 105 ret = 0; 106 break; 107 case FAN_DENY: 108 default: 109 ret = -EPERM; 110 } 111 event->response = 0; 112 spin_unlock(&event->lock); 113 114 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 115 group, event, ret); 116 117 return ret; 118 } 119 #endif 120 121 static int fanotify_handle_event(struct fsnotify_group *group, 122 struct fsnotify_mark *inode_mark, 123 struct fsnotify_mark *fanotify_mark, 124 struct fsnotify_event *event) 125 { 126 int ret = 0; 127 struct fsnotify_event *notify_event = NULL; 128 129 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 130 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 131 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 132 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 133 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 134 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 135 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 136 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 137 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 138 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 139 140 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 141 142 notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge); 143 if (IS_ERR(notify_event)) 144 return PTR_ERR(notify_event); 145 146 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 147 if (event->mask & FAN_ALL_PERM_EVENTS) { 148 /* if we merged we need to wait on the new event */ 149 if (notify_event) 150 event = notify_event; 151 ret = fanotify_get_response_from_access(group, event); 152 } 153 #endif 154 155 if (notify_event) 156 fsnotify_put_event(notify_event); 157 158 return ret; 159 } 160 161 static bool fanotify_should_send_event(struct fsnotify_group *group, 162 struct inode *to_tell, 163 struct fsnotify_mark *inode_mark, 164 struct fsnotify_mark *vfsmnt_mark, 165 __u32 event_mask, void *data, int data_type) 166 { 167 __u32 marks_mask, marks_ignored_mask; 168 struct path *path = data; 169 170 pr_debug("%s: group=%p to_tell=%p inode_mark=%p vfsmnt_mark=%p " 171 "mask=%x data=%p data_type=%d\n", __func__, group, to_tell, 172 inode_mark, vfsmnt_mark, event_mask, data, data_type); 173 174 /* if we don't have enough info to send an event to userspace say no */ 175 if (data_type != FSNOTIFY_EVENT_PATH) 176 return false; 177 178 /* sorry, fanotify only gives a damn about files and dirs */ 179 if (!S_ISREG(path->dentry->d_inode->i_mode) && 180 !S_ISDIR(path->dentry->d_inode->i_mode)) 181 return false; 182 183 if (inode_mark && vfsmnt_mark) { 184 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 185 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 186 } else if (inode_mark) { 187 /* 188 * if the event is for a child and this inode doesn't care about 189 * events on the child, don't send it! 190 */ 191 if ((event_mask & FS_EVENT_ON_CHILD) && 192 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 193 return false; 194 marks_mask = inode_mark->mask; 195 marks_ignored_mask = inode_mark->ignored_mask; 196 } else if (vfsmnt_mark) { 197 marks_mask = vfsmnt_mark->mask; 198 marks_ignored_mask = vfsmnt_mark->ignored_mask; 199 } else { 200 BUG(); 201 } 202 203 if (S_ISDIR(path->dentry->d_inode->i_mode) && 204 (marks_ignored_mask & FS_ISDIR)) 205 return false; 206 207 if (event_mask & marks_mask & ~marks_ignored_mask) 208 return true; 209 210 return false; 211 } 212 213 static void fanotify_free_group_priv(struct fsnotify_group *group) 214 { 215 struct user_struct *user; 216 217 user = group->fanotify_data.user; 218 atomic_dec(&user->fanotify_listeners); 219 free_uid(user); 220 } 221 222 const struct fsnotify_ops fanotify_fsnotify_ops = { 223 .handle_event = fanotify_handle_event, 224 .should_send_event = fanotify_should_send_event, 225 .free_group_priv = fanotify_free_group_priv, 226 .free_event_priv = NULL, 227 .freeing_mark = NULL, 228 }; 229