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 break; 25 case (FSNOTIFY_EVENT_NONE): 26 return true; 27 default: 28 BUG(); 29 }; 30 } 31 return false; 32 } 33 34 /* and the list better be locked by something too! */ 35 static struct fsnotify_event *fanotify_merge(struct list_head *list, 36 struct fsnotify_event *event) 37 { 38 struct fsnotify_event_holder *test_holder; 39 struct fsnotify_event *test_event = NULL; 40 struct fsnotify_event *new_event; 41 42 pr_debug("%s: list=%p event=%p\n", __func__, list, event); 43 44 45 list_for_each_entry_reverse(test_holder, list, event_list) { 46 if (should_merge(test_holder->event, event)) { 47 test_event = test_holder->event; 48 break; 49 } 50 } 51 52 if (!test_event) 53 return NULL; 54 55 fsnotify_get_event(test_event); 56 57 /* if they are exactly the same we are done */ 58 if (test_event->mask == event->mask) 59 return test_event; 60 61 /* 62 * if the refcnt == 2 this is the only queue 63 * for this event and so we can update the mask 64 * in place. 65 */ 66 if (atomic_read(&test_event->refcnt) == 2) { 67 test_event->mask |= event->mask; 68 return test_event; 69 } 70 71 new_event = fsnotify_clone_event(test_event); 72 73 /* done with test_event */ 74 fsnotify_put_event(test_event); 75 76 /* couldn't allocate memory, merge was not possible */ 77 if (unlikely(!new_event)) 78 return ERR_PTR(-ENOMEM); 79 80 /* build new event and replace it on the list */ 81 new_event->mask = (test_event->mask | event->mask); 82 fsnotify_replace_event(test_holder, new_event); 83 84 /* we hold a reference on new_event from clone_event */ 85 return new_event; 86 } 87 88 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 89 static int fanotify_get_response_from_access(struct fsnotify_group *group, 90 struct fsnotify_event *event) 91 { 92 int ret; 93 94 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 95 96 wait_event(group->fanotify_data.access_waitq, event->response || 97 atomic_read(&group->fanotify_data.bypass_perm)); 98 99 if (!event->response) /* bypass_perm set */ 100 return 0; 101 102 /* userspace responded, convert to something usable */ 103 spin_lock(&event->lock); 104 switch (event->response) { 105 case FAN_ALLOW: 106 ret = 0; 107 break; 108 case FAN_DENY: 109 default: 110 ret = -EPERM; 111 } 112 event->response = 0; 113 spin_unlock(&event->lock); 114 115 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 116 group, event, ret); 117 118 return ret; 119 } 120 #endif 121 122 static int fanotify_handle_event(struct fsnotify_group *group, 123 struct fsnotify_mark *inode_mark, 124 struct fsnotify_mark *fanotify_mark, 125 struct fsnotify_event *event) 126 { 127 int ret = 0; 128 struct fsnotify_event *notify_event = NULL; 129 130 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 131 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 132 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 133 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 134 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 135 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 136 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 137 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 138 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 139 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 140 141 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 142 143 notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge); 144 if (IS_ERR(notify_event)) 145 return PTR_ERR(notify_event); 146 147 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 148 if (event->mask & FAN_ALL_PERM_EVENTS) { 149 /* if we merged we need to wait on the new event */ 150 if (notify_event) 151 event = notify_event; 152 ret = fanotify_get_response_from_access(group, event); 153 } 154 #endif 155 156 if (notify_event) 157 fsnotify_put_event(notify_event); 158 159 return ret; 160 } 161 162 static bool fanotify_should_send_event(struct fsnotify_group *group, 163 struct inode *to_tell, 164 struct fsnotify_mark *inode_mark, 165 struct fsnotify_mark *vfsmnt_mark, 166 __u32 event_mask, void *data, int data_type) 167 { 168 __u32 marks_mask, marks_ignored_mask; 169 struct path *path = data; 170 171 pr_debug("%s: group=%p to_tell=%p inode_mark=%p vfsmnt_mark=%p " 172 "mask=%x data=%p data_type=%d\n", __func__, group, to_tell, 173 inode_mark, vfsmnt_mark, event_mask, data, data_type); 174 175 /* if we don't have enough info to send an event to userspace say no */ 176 if (data_type != FSNOTIFY_EVENT_PATH) 177 return false; 178 179 /* sorry, fanotify only gives a damn about files and dirs */ 180 if (!S_ISREG(path->dentry->d_inode->i_mode) && 181 !S_ISDIR(path->dentry->d_inode->i_mode)) 182 return false; 183 184 if (inode_mark && vfsmnt_mark) { 185 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 186 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 187 } else if (inode_mark) { 188 /* 189 * if the event is for a child and this inode doesn't care about 190 * events on the child, don't send it! 191 */ 192 if ((event_mask & FS_EVENT_ON_CHILD) && 193 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 194 return false; 195 marks_mask = inode_mark->mask; 196 marks_ignored_mask = inode_mark->ignored_mask; 197 } else if (vfsmnt_mark) { 198 marks_mask = vfsmnt_mark->mask; 199 marks_ignored_mask = vfsmnt_mark->ignored_mask; 200 } else { 201 BUG(); 202 } 203 204 if (S_ISDIR(path->dentry->d_inode->i_mode) && 205 (marks_ignored_mask & FS_ISDIR)) 206 return false; 207 208 if (event_mask & marks_mask & ~marks_ignored_mask) 209 return true; 210 211 return false; 212 } 213 214 static void fanotify_free_group_priv(struct fsnotify_group *group) 215 { 216 struct user_struct *user; 217 218 user = group->fanotify_data.user; 219 atomic_dec(&user->fanotify_listeners); 220 free_uid(user); 221 } 222 223 const struct fsnotify_ops fanotify_fsnotify_ops = { 224 .handle_event = fanotify_handle_event, 225 .should_send_event = fanotify_should_send_event, 226 .free_group_priv = fanotify_free_group_priv, 227 .free_event_priv = NULL, 228 .freeing_mark = NULL, 229 }; 230