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/sched/user.h> 10 #include <linux/types.h> 11 #include <linux/wait.h> 12 13 #include "fanotify.h" 14 15 static bool should_merge(struct fsnotify_event *old_fsn, 16 struct fsnotify_event *new_fsn) 17 { 18 struct fanotify_event_info *old, *new; 19 20 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn); 21 old = FANOTIFY_E(old_fsn); 22 new = FANOTIFY_E(new_fsn); 23 24 if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid && 25 old->path.mnt == new->path.mnt && 26 old->path.dentry == new->path.dentry) 27 return true; 28 return false; 29 } 30 31 /* and the list better be locked by something too! */ 32 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) 33 { 34 struct fsnotify_event *test_event; 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 test_event->mask |= event->mask; 51 return 1; 52 } 53 } 54 55 return 0; 56 } 57 58 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 59 static int fanotify_get_response(struct fsnotify_group *group, 60 struct fanotify_perm_event_info *event, 61 struct fsnotify_iter_info *iter_info) 62 { 63 int ret; 64 65 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 66 67 /* 68 * fsnotify_prepare_user_wait() fails if we race with mark deletion. 69 * Just let the operation pass in that case. 70 */ 71 if (!fsnotify_prepare_user_wait(iter_info)) { 72 event->response = FAN_ALLOW; 73 goto out; 74 } 75 76 wait_event(group->fanotify_data.access_waitq, event->response); 77 78 fsnotify_finish_user_wait(iter_info); 79 out: 80 /* userspace responded, convert to something usable */ 81 switch (event->response) { 82 case FAN_ALLOW: 83 ret = 0; 84 break; 85 case FAN_DENY: 86 default: 87 ret = -EPERM; 88 } 89 event->response = 0; 90 91 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 92 group, event, ret); 93 94 return ret; 95 } 96 #endif 97 98 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 99 struct fsnotify_mark *vfsmnt_mark, 100 u32 event_mask, 101 const void *data, int data_type) 102 { 103 __u32 marks_mask, marks_ignored_mask; 104 const struct path *path = data; 105 106 pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p" 107 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark, 108 event_mask, data, data_type); 109 110 /* if we don't have enough info to send an event to userspace say no */ 111 if (data_type != FSNOTIFY_EVENT_PATH) 112 return false; 113 114 /* sorry, fanotify only gives a damn about files and dirs */ 115 if (!d_is_reg(path->dentry) && 116 !d_can_lookup(path->dentry)) 117 return false; 118 119 if (inode_mark && vfsmnt_mark) { 120 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 121 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 122 } else if (inode_mark) { 123 /* 124 * if the event is for a child and this inode doesn't care about 125 * events on the child, don't send it! 126 */ 127 if ((event_mask & FS_EVENT_ON_CHILD) && 128 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 129 return false; 130 marks_mask = inode_mark->mask; 131 marks_ignored_mask = inode_mark->ignored_mask; 132 } else if (vfsmnt_mark) { 133 marks_mask = vfsmnt_mark->mask; 134 marks_ignored_mask = vfsmnt_mark->ignored_mask; 135 } else { 136 BUG(); 137 } 138 139 if (d_is_dir(path->dentry) && 140 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 141 return false; 142 143 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask & 144 ~marks_ignored_mask) 145 return true; 146 147 return false; 148 } 149 150 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 151 const struct path *path) 152 { 153 struct fanotify_event_info *event; 154 155 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 156 if (mask & FAN_ALL_PERM_EVENTS) { 157 struct fanotify_perm_event_info *pevent; 158 159 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 160 GFP_KERNEL); 161 if (!pevent) 162 return NULL; 163 event = &pevent->fae; 164 pevent->response = 0; 165 goto init; 166 } 167 #endif 168 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 169 if (!event) 170 return NULL; 171 init: __maybe_unused 172 fsnotify_init_event(&event->fse, inode, mask); 173 event->tgid = get_pid(task_tgid(current)); 174 if (path) { 175 event->path = *path; 176 path_get(&event->path); 177 } else { 178 event->path.mnt = NULL; 179 event->path.dentry = NULL; 180 } 181 return event; 182 } 183 184 static int fanotify_handle_event(struct fsnotify_group *group, 185 struct inode *inode, 186 struct fsnotify_mark *inode_mark, 187 struct fsnotify_mark *fanotify_mark, 188 u32 mask, const void *data, int data_type, 189 const unsigned char *file_name, u32 cookie, 190 struct fsnotify_iter_info *iter_info) 191 { 192 int ret = 0; 193 struct fanotify_event_info *event; 194 struct fsnotify_event *fsn_event; 195 196 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 197 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 198 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 199 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 200 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 201 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 202 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 203 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 204 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 205 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 206 207 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 208 data_type)) 209 return 0; 210 211 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 212 mask); 213 214 event = fanotify_alloc_event(inode, mask, data); 215 if (unlikely(!event)) 216 return -ENOMEM; 217 218 fsn_event = &event->fse; 219 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 220 if (ret) { 221 /* Permission events shouldn't be merged */ 222 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 223 /* Our event wasn't used in the end. Free it. */ 224 fsnotify_destroy_event(group, fsn_event); 225 226 return 0; 227 } 228 229 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 230 if (mask & FAN_ALL_PERM_EVENTS) { 231 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), 232 iter_info); 233 fsnotify_destroy_event(group, fsn_event); 234 } 235 #endif 236 return ret; 237 } 238 239 static void fanotify_free_group_priv(struct fsnotify_group *group) 240 { 241 struct user_struct *user; 242 243 user = group->fanotify_data.user; 244 atomic_dec(&user->fanotify_listeners); 245 free_uid(user); 246 } 247 248 static void fanotify_free_event(struct fsnotify_event *fsn_event) 249 { 250 struct fanotify_event_info *event; 251 252 event = FANOTIFY_E(fsn_event); 253 path_put(&event->path); 254 put_pid(event->tgid); 255 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 256 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) { 257 kmem_cache_free(fanotify_perm_event_cachep, 258 FANOTIFY_PE(fsn_event)); 259 return; 260 } 261 #endif 262 kmem_cache_free(fanotify_event_cachep, event); 263 } 264 265 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark) 266 { 267 kmem_cache_free(fanotify_mark_cache, fsn_mark); 268 } 269 270 const struct fsnotify_ops fanotify_fsnotify_ops = { 271 .handle_event = fanotify_handle_event, 272 .free_group_priv = fanotify_free_group_priv, 273 .free_event = fanotify_free_event, 274 .free_mark = fanotify_free_mark, 275 }; 276