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 14 #include "fanotify.h" 15 16 static bool should_merge(struct fsnotify_event *old_fsn, 17 struct fsnotify_event *new_fsn) 18 { 19 struct fanotify_event_info *old, *new; 20 21 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn); 22 old = FANOTIFY_E(old_fsn); 23 new = FANOTIFY_E(new_fsn); 24 25 if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid && 26 old->path.mnt == new->path.mnt && 27 old->path.dentry == new->path.dentry) 28 return true; 29 return false; 30 } 31 32 /* and the list better be locked by something too! */ 33 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) 34 { 35 struct fsnotify_event *test_event; 36 37 pr_debug("%s: list=%p event=%p\n", __func__, list, event); 38 39 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 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 (event->mask & FAN_ALL_PERM_EVENTS) 46 return 0; 47 #endif 48 49 list_for_each_entry_reverse(test_event, list, list) { 50 if (should_merge(test_event, event)) { 51 test_event->mask |= event->mask; 52 return 1; 53 } 54 } 55 56 return 0; 57 } 58 59 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 60 static int fanotify_get_response(struct fsnotify_group *group, 61 struct fanotify_perm_event_info *event, 62 struct fsnotify_iter_info *iter_info) 63 { 64 int ret; 65 66 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 67 68 /* 69 * fsnotify_prepare_user_wait() fails if we race with mark deletion. 70 * Just let the operation pass in that case. 71 */ 72 if (!fsnotify_prepare_user_wait(iter_info)) { 73 event->response = FAN_ALLOW; 74 goto out; 75 } 76 77 wait_event(group->fanotify_data.access_waitq, event->response); 78 79 fsnotify_finish_user_wait(iter_info); 80 out: 81 /* userspace responded, convert to something usable */ 82 switch (event->response) { 83 case FAN_ALLOW: 84 ret = 0; 85 break; 86 case FAN_DENY: 87 default: 88 ret = -EPERM; 89 } 90 event->response = 0; 91 92 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 93 group, event, ret); 94 95 return ret; 96 } 97 #endif 98 99 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 100 struct fsnotify_mark *vfsmnt_mark, 101 u32 event_mask, 102 const void *data, int data_type) 103 { 104 __u32 marks_mask, marks_ignored_mask; 105 const struct path *path = data; 106 107 pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p" 108 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark, 109 event_mask, data, data_type); 110 111 /* if we don't have enough info to send an event to userspace say no */ 112 if (data_type != FSNOTIFY_EVENT_PATH) 113 return false; 114 115 /* sorry, fanotify only gives a damn about files and dirs */ 116 if (!d_is_reg(path->dentry) && 117 !d_can_lookup(path->dentry)) 118 return false; 119 120 if (inode_mark && vfsmnt_mark) { 121 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 122 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 123 } else if (inode_mark) { 124 /* 125 * if the event is for a child and this inode doesn't care about 126 * events on the child, don't send it! 127 */ 128 if ((event_mask & FS_EVENT_ON_CHILD) && 129 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 130 return false; 131 marks_mask = inode_mark->mask; 132 marks_ignored_mask = inode_mark->ignored_mask; 133 } else if (vfsmnt_mark) { 134 marks_mask = vfsmnt_mark->mask; 135 marks_ignored_mask = vfsmnt_mark->ignored_mask; 136 } else { 137 BUG(); 138 } 139 140 if (d_is_dir(path->dentry) && 141 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 142 return false; 143 144 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask & 145 ~marks_ignored_mask) 146 return true; 147 148 return false; 149 } 150 151 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 152 const struct path *path) 153 { 154 struct fanotify_event_info *event; 155 156 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 157 if (mask & FAN_ALL_PERM_EVENTS) { 158 struct fanotify_perm_event_info *pevent; 159 160 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 161 GFP_KERNEL); 162 if (!pevent) 163 return NULL; 164 event = &pevent->fae; 165 pevent->response = 0; 166 goto init; 167 } 168 #endif 169 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 170 if (!event) 171 return NULL; 172 init: __maybe_unused 173 fsnotify_init_event(&event->fse, inode, mask); 174 event->tgid = get_pid(task_tgid(current)); 175 if (path) { 176 event->path = *path; 177 path_get(&event->path); 178 } else { 179 event->path.mnt = NULL; 180 event->path.dentry = NULL; 181 } 182 return event; 183 } 184 185 static int fanotify_handle_event(struct fsnotify_group *group, 186 struct inode *inode, 187 struct fsnotify_mark *inode_mark, 188 struct fsnotify_mark *fanotify_mark, 189 u32 mask, const void *data, int data_type, 190 const unsigned char *file_name, u32 cookie, 191 struct fsnotify_iter_info *iter_info) 192 { 193 int ret = 0; 194 struct fanotify_event_info *event; 195 struct fsnotify_event *fsn_event; 196 197 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 198 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 199 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 200 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 201 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 202 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 203 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 204 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 205 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 206 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 207 208 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 209 data_type)) 210 return 0; 211 212 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 213 mask); 214 215 event = fanotify_alloc_event(inode, mask, data); 216 if (unlikely(!event)) 217 return -ENOMEM; 218 219 fsn_event = &event->fse; 220 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 221 if (ret) { 222 /* Permission events shouldn't be merged */ 223 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 224 /* Our event wasn't used in the end. Free it. */ 225 fsnotify_destroy_event(group, fsn_event); 226 227 return 0; 228 } 229 230 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 231 if (mask & FAN_ALL_PERM_EVENTS) { 232 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), 233 iter_info); 234 fsnotify_destroy_event(group, fsn_event); 235 } 236 #endif 237 return ret; 238 } 239 240 static void fanotify_free_group_priv(struct fsnotify_group *group) 241 { 242 struct user_struct *user; 243 244 user = group->fanotify_data.user; 245 atomic_dec(&user->fanotify_listeners); 246 free_uid(user); 247 } 248 249 static void fanotify_free_event(struct fsnotify_event *fsn_event) 250 { 251 struct fanotify_event_info *event; 252 253 event = FANOTIFY_E(fsn_event); 254 path_put(&event->path); 255 put_pid(event->tgid); 256 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 257 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) { 258 kmem_cache_free(fanotify_perm_event_cachep, 259 FANOTIFY_PE(fsn_event)); 260 return; 261 } 262 #endif 263 kmem_cache_free(fanotify_event_cachep, event); 264 } 265 266 static void fanotify_free_mark(struct fsnotify_mark *fsn_mark) 267 { 268 kmem_cache_free(fanotify_mark_cache, fsn_mark); 269 } 270 271 const struct fsnotify_ops fanotify_fsnotify_ops = { 272 .handle_event = fanotify_handle_event, 273 .free_group_priv = fanotify_free_group_priv, 274 .free_event = fanotify_free_event, 275 .free_mark = fanotify_free_mark, 276 }; 277