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 35 pr_debug("%s: list=%p event=%p\n", __func__, list, event); 36 37 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 38 /* 39 * Don't merge a permission event with any other event so that we know 40 * the event structure we have created in fanotify_handle_event() is the 41 * one we should check for permission response. 42 */ 43 if (event->mask & FAN_ALL_PERM_EVENTS) 44 return 0; 45 #endif 46 47 list_for_each_entry_reverse(test_event, list, list) { 48 if (should_merge(test_event, event)) { 49 test_event->mask |= event->mask; 50 return 1; 51 } 52 } 53 54 return 0; 55 } 56 57 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 58 static int fanotify_get_response(struct fsnotify_group *group, 59 struct fanotify_perm_event_info *event) 60 { 61 int ret; 62 63 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 64 65 wait_event(group->fanotify_data.access_waitq, event->response); 66 67 /* userspace responded, convert to something usable */ 68 switch (event->response) { 69 case FAN_ALLOW: 70 ret = 0; 71 break; 72 case FAN_DENY: 73 default: 74 ret = -EPERM; 75 } 76 event->response = 0; 77 78 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 79 group, event, ret); 80 81 return ret; 82 } 83 #endif 84 85 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 86 struct fsnotify_mark *vfsmnt_mark, 87 u32 event_mask, 88 const void *data, int data_type) 89 { 90 __u32 marks_mask, marks_ignored_mask; 91 const struct path *path = data; 92 93 pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p" 94 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark, 95 event_mask, data, data_type); 96 97 /* if we don't have enough info to send an event to userspace say no */ 98 if (data_type != FSNOTIFY_EVENT_PATH) 99 return false; 100 101 /* sorry, fanotify only gives a damn about files and dirs */ 102 if (!d_is_reg(path->dentry) && 103 !d_can_lookup(path->dentry)) 104 return false; 105 106 if (inode_mark && vfsmnt_mark) { 107 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 108 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 109 } else if (inode_mark) { 110 /* 111 * if the event is for a child and this inode doesn't care about 112 * events on the child, don't send it! 113 */ 114 if ((event_mask & FS_EVENT_ON_CHILD) && 115 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 116 return false; 117 marks_mask = inode_mark->mask; 118 marks_ignored_mask = inode_mark->ignored_mask; 119 } else if (vfsmnt_mark) { 120 marks_mask = vfsmnt_mark->mask; 121 marks_ignored_mask = vfsmnt_mark->ignored_mask; 122 } else { 123 BUG(); 124 } 125 126 if (d_is_dir(path->dentry) && 127 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 128 return false; 129 130 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask & 131 ~marks_ignored_mask) 132 return true; 133 134 return false; 135 } 136 137 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 138 const struct path *path) 139 { 140 struct fanotify_event_info *event; 141 142 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 143 if (mask & FAN_ALL_PERM_EVENTS) { 144 struct fanotify_perm_event_info *pevent; 145 146 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 147 GFP_KERNEL); 148 if (!pevent) 149 return NULL; 150 event = &pevent->fae; 151 pevent->response = 0; 152 goto init; 153 } 154 #endif 155 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 156 if (!event) 157 return NULL; 158 init: __maybe_unused 159 fsnotify_init_event(&event->fse, inode, mask); 160 event->tgid = get_pid(task_tgid(current)); 161 if (path) { 162 event->path = *path; 163 path_get(&event->path); 164 } else { 165 event->path.mnt = NULL; 166 event->path.dentry = NULL; 167 } 168 return event; 169 } 170 171 static int fanotify_handle_event(struct fsnotify_group *group, 172 struct inode *inode, 173 struct fsnotify_mark *inode_mark, 174 struct fsnotify_mark *fanotify_mark, 175 u32 mask, const void *data, int data_type, 176 const unsigned char *file_name, u32 cookie) 177 { 178 int ret = 0; 179 struct fanotify_event_info *event; 180 struct fsnotify_event *fsn_event; 181 182 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 183 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 184 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 185 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 186 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 187 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 188 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 189 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 190 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 191 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 192 193 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 194 data_type)) 195 return 0; 196 197 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 198 mask); 199 200 event = fanotify_alloc_event(inode, mask, data); 201 if (unlikely(!event)) 202 return -ENOMEM; 203 204 fsn_event = &event->fse; 205 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 206 if (ret) { 207 /* Permission events shouldn't be merged */ 208 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 209 /* Our event wasn't used in the end. Free it. */ 210 fsnotify_destroy_event(group, fsn_event); 211 212 return 0; 213 } 214 215 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 216 if (mask & FAN_ALL_PERM_EVENTS) { 217 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event)); 218 fsnotify_destroy_event(group, fsn_event); 219 } 220 #endif 221 return ret; 222 } 223 224 static void fanotify_free_group_priv(struct fsnotify_group *group) 225 { 226 struct user_struct *user; 227 228 user = group->fanotify_data.user; 229 atomic_dec(&user->fanotify_listeners); 230 free_uid(user); 231 } 232 233 static void fanotify_free_event(struct fsnotify_event *fsn_event) 234 { 235 struct fanotify_event_info *event; 236 237 event = FANOTIFY_E(fsn_event); 238 path_put(&event->path); 239 put_pid(event->tgid); 240 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 241 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) { 242 kmem_cache_free(fanotify_perm_event_cachep, 243 FANOTIFY_PE(fsn_event)); 244 return; 245 } 246 #endif 247 kmem_cache_free(fanotify_event_cachep, event); 248 } 249 250 const struct fsnotify_ops fanotify_fsnotify_ops = { 251 .handle_event = fanotify_handle_event, 252 .free_group_priv = fanotify_free_group_priv, 253 .free_event = fanotify_free_event, 254 }; 255