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/types.h> 12 #include <linux/wait.h> 13 #include <linux/audit.h> 14 15 #include "fanotify.h" 16 17 static bool should_merge(struct fsnotify_event *old_fsn, 18 struct fsnotify_event *new_fsn) 19 { 20 struct fanotify_event_info *old, *new; 21 22 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn); 23 old = FANOTIFY_E(old_fsn); 24 new = FANOTIFY_E(new_fsn); 25 26 if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid && 27 old->path.mnt == new->path.mnt && 28 old->path.dentry == new->path.dentry) 29 return true; 30 return false; 31 } 32 33 /* and the list better be locked by something too! */ 34 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) 35 { 36 struct fsnotify_event *test_event; 37 38 pr_debug("%s: list=%p event=%p\n", __func__, list, event); 39 40 /* 41 * Don't merge a permission event with any other event so that we know 42 * the event structure we have created in fanotify_handle_event() is the 43 * one we should check for permission response. 44 */ 45 if (fanotify_is_perm_event(event->mask)) 46 return 0; 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 static int fanotify_get_response(struct fsnotify_group *group, 59 struct fanotify_perm_event_info *event, 60 struct fsnotify_iter_info *iter_info) 61 { 62 int ret; 63 64 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 65 66 wait_event(group->fanotify_data.access_waitq, event->response); 67 68 /* userspace responded, convert to something usable */ 69 switch (event->response & ~FAN_AUDIT) { 70 case FAN_ALLOW: 71 ret = 0; 72 break; 73 case FAN_DENY: 74 default: 75 ret = -EPERM; 76 } 77 78 /* Check if the response should be audited */ 79 if (event->response & FAN_AUDIT) 80 audit_fanotify(event->response & ~FAN_AUDIT); 81 82 event->response = 0; 83 84 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 85 group, event, ret); 86 87 return ret; 88 } 89 90 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 91 struct fsnotify_mark *vfsmnt_mark, 92 u32 event_mask, 93 const void *data, int data_type) 94 { 95 __u32 marks_mask = 0, marks_ignored_mask = 0; 96 const 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 (!d_is_reg(path->dentry) && 108 !d_can_lookup(path->dentry)) 109 return false; 110 111 /* 112 * if the event is for a child and this inode doesn't care about 113 * events on the child, don't send it! 114 */ 115 if (inode_mark && 116 (!(event_mask & FS_EVENT_ON_CHILD) || 117 (inode_mark->mask & FS_EVENT_ON_CHILD))) { 118 marks_mask |= inode_mark->mask; 119 marks_ignored_mask |= inode_mark->ignored_mask; 120 } 121 122 if (vfsmnt_mark) { 123 marks_mask |= vfsmnt_mark->mask; 124 marks_ignored_mask |= vfsmnt_mark->ignored_mask; 125 } 126 127 if (d_is_dir(path->dentry) && 128 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 129 return false; 130 131 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask & 132 ~marks_ignored_mask) 133 return true; 134 135 return false; 136 } 137 138 struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group, 139 struct inode *inode, u32 mask, 140 const struct path *path) 141 { 142 struct fanotify_event_info *event; 143 gfp_t gfp = GFP_KERNEL; 144 145 /* 146 * For queues with unlimited length lost events are not expected and 147 * can possibly have security implications. Avoid losing events when 148 * memory is short. 149 */ 150 if (group->max_events == UINT_MAX) 151 gfp |= __GFP_NOFAIL; 152 153 if (fanotify_is_perm_event(mask)) { 154 struct fanotify_perm_event_info *pevent; 155 156 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp); 157 if (!pevent) 158 return NULL; 159 event = &pevent->fae; 160 pevent->response = 0; 161 goto init; 162 } 163 event = kmem_cache_alloc(fanotify_event_cachep, gfp); 164 if (!event) 165 return NULL; 166 init: __maybe_unused 167 fsnotify_init_event(&event->fse, inode, mask); 168 event->tgid = get_pid(task_tgid(current)); 169 if (path) { 170 event->path = *path; 171 path_get(&event->path); 172 } else { 173 event->path.mnt = NULL; 174 event->path.dentry = NULL; 175 } 176 return event; 177 } 178 179 static int fanotify_handle_event(struct fsnotify_group *group, 180 struct inode *inode, 181 struct fsnotify_mark *inode_mark, 182 struct fsnotify_mark *fanotify_mark, 183 u32 mask, const void *data, int data_type, 184 const unsigned char *file_name, u32 cookie, 185 struct fsnotify_iter_info *iter_info) 186 { 187 int ret = 0; 188 struct fanotify_event_info *event; 189 struct fsnotify_event *fsn_event; 190 191 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 192 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 193 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 194 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 195 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 196 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 197 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 198 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 199 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 200 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 201 202 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 203 data_type)) 204 return 0; 205 206 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 207 mask); 208 209 if (fanotify_is_perm_event(mask)) { 210 /* 211 * fsnotify_prepare_user_wait() fails if we race with mark 212 * deletion. Just let the operation pass in that case. 213 */ 214 if (!fsnotify_prepare_user_wait(iter_info)) 215 return 0; 216 } 217 218 event = fanotify_alloc_event(group, inode, mask, data); 219 ret = -ENOMEM; 220 if (unlikely(!event)) { 221 /* 222 * We don't queue overflow events for permission events as 223 * there the access is denied and so no event is in fact lost. 224 */ 225 if (!fanotify_is_perm_event(mask)) 226 fsnotify_queue_overflow(group); 227 goto finish; 228 } 229 230 fsn_event = &event->fse; 231 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 232 if (ret) { 233 /* Permission events shouldn't be merged */ 234 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 235 /* Our event wasn't used in the end. Free it. */ 236 fsnotify_destroy_event(group, fsn_event); 237 238 ret = 0; 239 } else if (fanotify_is_perm_event(mask)) { 240 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), 241 iter_info); 242 fsnotify_destroy_event(group, fsn_event); 243 } 244 finish: 245 if (fanotify_is_perm_event(mask)) 246 fsnotify_finish_user_wait(iter_info); 247 248 return ret; 249 } 250 251 static void fanotify_free_group_priv(struct fsnotify_group *group) 252 { 253 struct user_struct *user; 254 255 user = group->fanotify_data.user; 256 atomic_dec(&user->fanotify_listeners); 257 free_uid(user); 258 } 259 260 static void fanotify_free_event(struct fsnotify_event *fsn_event) 261 { 262 struct fanotify_event_info *event; 263 264 event = FANOTIFY_E(fsn_event); 265 path_put(&event->path); 266 put_pid(event->tgid); 267 if (fanotify_is_perm_event(fsn_event->mask)) { 268 kmem_cache_free(fanotify_perm_event_cachep, 269 FANOTIFY_PE(fsn_event)); 270 return; 271 } 272 kmem_cache_free(fanotify_event_cachep, event); 273 } 274 275 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark) 276 { 277 kmem_cache_free(fanotify_mark_cache, fsn_mark); 278 } 279 280 const struct fsnotify_ops fanotify_fsnotify_ops = { 281 .handle_event = fanotify_handle_event, 282 .free_group_priv = fanotify_free_group_priv, 283 .free_event = fanotify_free_event, 284 .free_mark = fanotify_free_mark, 285 }; 286