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