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 72 /* userspace responded, convert to something usable */ 73 switch (event->response) { 74 case FAN_ALLOW: 75 ret = 0; 76 break; 77 case FAN_DENY: 78 default: 79 ret = -EPERM; 80 } 81 event->response = 0; 82 83 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 84 group, event, ret); 85 86 return ret; 87 } 88 #endif 89 90 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 91 struct fsnotify_mark *vfsmnt_mark, 92 u32 event_mask, 93 void *data, int data_type) 94 { 95 __u32 marks_mask, marks_ignored_mask; 96 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 if (inode_mark && vfsmnt_mark) { 112 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 113 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 114 } else if (inode_mark) { 115 /* 116 * if the event is for a child and this inode doesn't care about 117 * events on the child, don't send it! 118 */ 119 if ((event_mask & FS_EVENT_ON_CHILD) && 120 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 121 return false; 122 marks_mask = inode_mark->mask; 123 marks_ignored_mask = inode_mark->ignored_mask; 124 } else if (vfsmnt_mark) { 125 marks_mask = vfsmnt_mark->mask; 126 marks_ignored_mask = vfsmnt_mark->ignored_mask; 127 } else { 128 BUG(); 129 } 130 131 if (d_is_dir(path->dentry) && 132 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 133 return false; 134 135 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask & 136 ~marks_ignored_mask) 137 return true; 138 139 return false; 140 } 141 142 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 143 struct path *path) 144 { 145 struct fanotify_event_info *event; 146 147 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 148 if (mask & FAN_ALL_PERM_EVENTS) { 149 struct fanotify_perm_event_info *pevent; 150 151 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 152 GFP_KERNEL); 153 if (!pevent) 154 return NULL; 155 event = &pevent->fae; 156 pevent->response = 0; 157 goto init; 158 } 159 #endif 160 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 161 if (!event) 162 return NULL; 163 init: __maybe_unused 164 fsnotify_init_event(&event->fse, inode, mask); 165 event->tgid = get_pid(task_tgid(current)); 166 if (path) { 167 event->path = *path; 168 path_get(&event->path); 169 } else { 170 event->path.mnt = NULL; 171 event->path.dentry = NULL; 172 } 173 return event; 174 } 175 176 static int fanotify_handle_event(struct fsnotify_group *group, 177 struct inode *inode, 178 struct fsnotify_mark *inode_mark, 179 struct fsnotify_mark *fanotify_mark, 180 u32 mask, void *data, int data_type, 181 const unsigned char *file_name, u32 cookie) 182 { 183 int ret = 0; 184 struct fanotify_event_info *event; 185 struct fsnotify_event *fsn_event; 186 187 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 188 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 189 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 190 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 191 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 192 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 193 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 194 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 195 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 196 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 197 198 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 199 data_type)) 200 return 0; 201 202 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 203 mask); 204 205 event = fanotify_alloc_event(inode, mask, data); 206 if (unlikely(!event)) 207 return -ENOMEM; 208 209 fsn_event = &event->fse; 210 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 211 if (ret) { 212 /* Permission events shouldn't be merged */ 213 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 214 /* Our event wasn't used in the end. Free it. */ 215 fsnotify_destroy_event(group, fsn_event); 216 217 return 0; 218 } 219 220 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 221 if (mask & FAN_ALL_PERM_EVENTS) { 222 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event)); 223 fsnotify_destroy_event(group, fsn_event); 224 } 225 #endif 226 return ret; 227 } 228 229 static void fanotify_free_group_priv(struct fsnotify_group *group) 230 { 231 struct user_struct *user; 232 233 user = group->fanotify_data.user; 234 atomic_dec(&user->fanotify_listeners); 235 free_uid(user); 236 } 237 238 static void fanotify_free_event(struct fsnotify_event *fsn_event) 239 { 240 struct fanotify_event_info *event; 241 242 event = FANOTIFY_E(fsn_event); 243 path_put(&event->path); 244 put_pid(event->tgid); 245 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 246 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) { 247 kmem_cache_free(fanotify_perm_event_cachep, 248 FANOTIFY_PE(fsn_event)); 249 return; 250 } 251 #endif 252 kmem_cache_free(fanotify_event_cachep, event); 253 } 254 255 const struct fsnotify_ops fanotify_fsnotify_ops = { 256 .handle_event = fanotify_handle_event, 257 .free_group_priv = fanotify_free_group_priv, 258 .free_event = fanotify_free_event, 259 }; 260