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 (!S_ISREG(path->dentry->d_inode->i_mode) && 119 !S_ISDIR(path->dentry->d_inode->i_mode)) 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 (S_ISDIR(path->dentry->d_inode->i_mode) && 143 (marks_ignored_mask & FS_ISDIR)) 144 return false; 145 146 if (event_mask & marks_mask & ~marks_ignored_mask) 147 return true; 148 149 return false; 150 } 151 152 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 153 struct path *path) 154 { 155 struct fanotify_event_info *event; 156 157 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 158 if (mask & FAN_ALL_PERM_EVENTS) { 159 struct fanotify_perm_event_info *pevent; 160 161 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 162 GFP_KERNEL); 163 if (!pevent) 164 return NULL; 165 event = &pevent->fae; 166 pevent->response = 0; 167 goto init; 168 } 169 #endif 170 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 171 if (!event) 172 return NULL; 173 init: __maybe_unused 174 fsnotify_init_event(&event->fse, inode, mask); 175 event->tgid = get_pid(task_tgid(current)); 176 if (path) { 177 event->path = *path; 178 path_get(&event->path); 179 } else { 180 event->path.mnt = NULL; 181 event->path.dentry = NULL; 182 } 183 return event; 184 } 185 186 static int fanotify_handle_event(struct fsnotify_group *group, 187 struct inode *inode, 188 struct fsnotify_mark *inode_mark, 189 struct fsnotify_mark *fanotify_mark, 190 u32 mask, void *data, int data_type, 191 const unsigned char *file_name, u32 cookie) 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 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 const struct fsnotify_ops fanotify_fsnotify_ops = { 266 .handle_event = fanotify_handle_event, 267 .free_group_priv = fanotify_free_group_priv, 268 .free_event = fanotify_free_event, 269 }; 270