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 return 0; 75 76 /* userspace responded, convert to something usable */ 77 switch (event->response) { 78 case FAN_ALLOW: 79 ret = 0; 80 break; 81 case FAN_DENY: 82 default: 83 ret = -EPERM; 84 } 85 event->response = 0; 86 87 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 88 group, event, ret); 89 90 return ret; 91 } 92 #endif 93 94 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 95 struct fsnotify_mark *vfsmnt_mark, 96 u32 event_mask, 97 void *data, int data_type) 98 { 99 __u32 marks_mask, marks_ignored_mask; 100 struct path *path = data; 101 102 pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p" 103 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark, 104 event_mask, data, data_type); 105 106 /* if we don't have enough info to send an event to userspace say no */ 107 if (data_type != FSNOTIFY_EVENT_PATH) 108 return false; 109 110 /* sorry, fanotify only gives a damn about files and dirs */ 111 if (!S_ISREG(path->dentry->d_inode->i_mode) && 112 !S_ISDIR(path->dentry->d_inode->i_mode)) 113 return false; 114 115 if (inode_mark && vfsmnt_mark) { 116 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 117 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 118 } else if (inode_mark) { 119 /* 120 * if the event is for a child and this inode doesn't care about 121 * events on the child, don't send it! 122 */ 123 if ((event_mask & FS_EVENT_ON_CHILD) && 124 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 125 return false; 126 marks_mask = inode_mark->mask; 127 marks_ignored_mask = inode_mark->ignored_mask; 128 } else if (vfsmnt_mark) { 129 marks_mask = vfsmnt_mark->mask; 130 marks_ignored_mask = vfsmnt_mark->ignored_mask; 131 } else { 132 BUG(); 133 } 134 135 if (S_ISDIR(path->dentry->d_inode->i_mode) && 136 (marks_ignored_mask & FS_ISDIR)) 137 return false; 138 139 if (event_mask & marks_mask & ~marks_ignored_mask) 140 return true; 141 142 return false; 143 } 144 145 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 146 struct path *path) 147 { 148 struct fanotify_event_info *event; 149 150 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 151 if (mask & FAN_ALL_PERM_EVENTS) { 152 struct fanotify_perm_event_info *pevent; 153 154 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 155 GFP_KERNEL); 156 if (!pevent) 157 return NULL; 158 event = &pevent->fae; 159 pevent->response = 0; 160 goto init; 161 } 162 #endif 163 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 164 if (!event) 165 return NULL; 166 init: __maybe_unused 167 fsnotify_init_event(&event->fse, inode, mask); 168 event->tgid = get_pid(task_tgid(current)); 169 if (path) { 170 event->path = *path; 171 path_get(&event->path); 172 } else { 173 event->path.mnt = NULL; 174 event->path.dentry = NULL; 175 } 176 return event; 177 } 178 179 static int fanotify_handle_event(struct fsnotify_group *group, 180 struct inode *inode, 181 struct fsnotify_mark *inode_mark, 182 struct fsnotify_mark *fanotify_mark, 183 u32 mask, void *data, int data_type, 184 const unsigned char *file_name, u32 cookie) 185 { 186 int ret = 0; 187 struct fanotify_event_info *event; 188 struct fsnotify_event *fsn_event; 189 190 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 191 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 192 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 193 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 194 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 195 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 196 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 197 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 198 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 199 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 200 201 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 202 data_type)) 203 return 0; 204 205 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 206 mask); 207 208 event = fanotify_alloc_event(inode, mask, data); 209 if (unlikely(!event)) 210 return -ENOMEM; 211 212 fsn_event = &event->fse; 213 ret = fsnotify_add_notify_event(group, fsn_event, fanotify_merge); 214 if (ret) { 215 /* Permission events shouldn't be merged */ 216 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 217 /* Our event wasn't used in the end. Free it. */ 218 fsnotify_destroy_event(group, fsn_event); 219 220 return 0; 221 } 222 223 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 224 if (mask & FAN_ALL_PERM_EVENTS) { 225 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event)); 226 fsnotify_destroy_event(group, fsn_event); 227 } 228 #endif 229 return ret; 230 } 231 232 static void fanotify_free_group_priv(struct fsnotify_group *group) 233 { 234 struct user_struct *user; 235 236 user = group->fanotify_data.user; 237 atomic_dec(&user->fanotify_listeners); 238 free_uid(user); 239 } 240 241 static void fanotify_free_event(struct fsnotify_event *fsn_event) 242 { 243 struct fanotify_event_info *event; 244 245 event = FANOTIFY_E(fsn_event); 246 path_put(&event->path); 247 put_pid(event->tgid); 248 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 249 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) { 250 kmem_cache_free(fanotify_perm_event_cachep, 251 FANOTIFY_PE(fsn_event)); 252 return; 253 } 254 #endif 255 kmem_cache_free(fanotify_event_cachep, event); 256 } 257 258 const struct fsnotify_ops fanotify_fsnotify_ops = { 259 .handle_event = fanotify_handle_event, 260 .free_group_priv = fanotify_free_group_priv, 261 .free_event = fanotify_free_event, 262 }; 263