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/sched/user.h> 10 #include <linux/types.h> 11 #include <linux/wait.h> 12 13 #include "fanotify.h" 14 15 static bool should_merge(struct fsnotify_event *old_fsn, 16 struct fsnotify_event *new_fsn) 17 { 18 struct fanotify_event_info *old, *new; 19 20 pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn); 21 old = FANOTIFY_E(old_fsn); 22 new = FANOTIFY_E(new_fsn); 23 24 if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid && 25 old->path.mnt == new->path.mnt && 26 old->path.dentry == new->path.dentry) 27 return true; 28 return false; 29 } 30 31 /* and the list better be locked by something too! */ 32 static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) 33 { 34 struct fsnotify_event *test_event; 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 test_event->mask |= event->mask; 51 return 1; 52 } 53 } 54 55 return 0; 56 } 57 58 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 59 static int fanotify_get_response(struct fsnotify_group *group, 60 struct fanotify_perm_event_info *event) 61 { 62 int ret; 63 64 pr_debug("%s: group=%p event=%p\n", __func__, group, event); 65 66 wait_event(group->fanotify_data.access_waitq, event->response); 67 68 /* userspace responded, convert to something usable */ 69 switch (event->response) { 70 case FAN_ALLOW: 71 ret = 0; 72 break; 73 case FAN_DENY: 74 default: 75 ret = -EPERM; 76 } 77 event->response = 0; 78 79 pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, 80 group, event, ret); 81 82 return ret; 83 } 84 #endif 85 86 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark, 87 struct fsnotify_mark *vfsmnt_mark, 88 u32 event_mask, 89 const void *data, int data_type) 90 { 91 __u32 marks_mask, marks_ignored_mask; 92 const struct path *path = data; 93 94 pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p" 95 " data_type=%d\n", __func__, inode_mark, vfsmnt_mark, 96 event_mask, data, data_type); 97 98 /* if we don't have enough info to send an event to userspace say no */ 99 if (data_type != FSNOTIFY_EVENT_PATH) 100 return false; 101 102 /* sorry, fanotify only gives a damn about files and dirs */ 103 if (!d_is_reg(path->dentry) && 104 !d_can_lookup(path->dentry)) 105 return false; 106 107 if (inode_mark && vfsmnt_mark) { 108 marks_mask = (vfsmnt_mark->mask | inode_mark->mask); 109 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask); 110 } else if (inode_mark) { 111 /* 112 * if the event is for a child and this inode doesn't care about 113 * events on the child, don't send it! 114 */ 115 if ((event_mask & FS_EVENT_ON_CHILD) && 116 !(inode_mark->mask & FS_EVENT_ON_CHILD)) 117 return false; 118 marks_mask = inode_mark->mask; 119 marks_ignored_mask = inode_mark->ignored_mask; 120 } else if (vfsmnt_mark) { 121 marks_mask = vfsmnt_mark->mask; 122 marks_ignored_mask = vfsmnt_mark->ignored_mask; 123 } else { 124 BUG(); 125 } 126 127 if (d_is_dir(path->dentry) && 128 !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) 129 return false; 130 131 if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask & 132 ~marks_ignored_mask) 133 return true; 134 135 return false; 136 } 137 138 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask, 139 const struct path *path) 140 { 141 struct fanotify_event_info *event; 142 143 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 144 if (mask & FAN_ALL_PERM_EVENTS) { 145 struct fanotify_perm_event_info *pevent; 146 147 pevent = kmem_cache_alloc(fanotify_perm_event_cachep, 148 GFP_KERNEL); 149 if (!pevent) 150 return NULL; 151 event = &pevent->fae; 152 pevent->response = 0; 153 goto init; 154 } 155 #endif 156 event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL); 157 if (!event) 158 return NULL; 159 init: __maybe_unused 160 fsnotify_init_event(&event->fse, inode, mask); 161 event->tgid = get_pid(task_tgid(current)); 162 if (path) { 163 event->path = *path; 164 path_get(&event->path); 165 } else { 166 event->path.mnt = NULL; 167 event->path.dentry = NULL; 168 } 169 return event; 170 } 171 172 static int fanotify_handle_event(struct fsnotify_group *group, 173 struct inode *inode, 174 struct fsnotify_mark *inode_mark, 175 struct fsnotify_mark *fanotify_mark, 176 u32 mask, const void *data, int data_type, 177 const unsigned char *file_name, u32 cookie) 178 { 179 int ret = 0; 180 struct fanotify_event_info *event; 181 struct fsnotify_event *fsn_event; 182 183 BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS); 184 BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY); 185 BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE); 186 BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE); 187 BUILD_BUG_ON(FAN_OPEN != FS_OPEN); 188 BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD); 189 BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW); 190 BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); 191 BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); 192 BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); 193 194 if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data, 195 data_type)) 196 return 0; 197 198 pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, 199 mask); 200 201 event = fanotify_alloc_event(inode, mask, data); 202 if (unlikely(!event)) 203 return -ENOMEM; 204 205 fsn_event = &event->fse; 206 ret = fsnotify_add_event(group, fsn_event, fanotify_merge); 207 if (ret) { 208 /* Permission events shouldn't be merged */ 209 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS); 210 /* Our event wasn't used in the end. Free it. */ 211 fsnotify_destroy_event(group, fsn_event); 212 213 return 0; 214 } 215 216 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 217 if (mask & FAN_ALL_PERM_EVENTS) { 218 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event)); 219 fsnotify_destroy_event(group, fsn_event); 220 } 221 #endif 222 return ret; 223 } 224 225 static void fanotify_free_group_priv(struct fsnotify_group *group) 226 { 227 struct user_struct *user; 228 229 user = group->fanotify_data.user; 230 atomic_dec(&user->fanotify_listeners); 231 free_uid(user); 232 } 233 234 static void fanotify_free_event(struct fsnotify_event *fsn_event) 235 { 236 struct fanotify_event_info *event; 237 238 event = FANOTIFY_E(fsn_event); 239 path_put(&event->path); 240 put_pid(event->tgid); 241 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS 242 if (fsn_event->mask & FAN_ALL_PERM_EVENTS) { 243 kmem_cache_free(fanotify_perm_event_cachep, 244 FANOTIFY_PE(fsn_event)); 245 return; 246 } 247 #endif 248 kmem_cache_free(fanotify_event_cachep, event); 249 } 250 251 const struct fsnotify_ops fanotify_fsnotify_ops = { 252 .handle_event = fanotify_handle_event, 253 .free_group_priv = fanotify_free_group_priv, 254 .free_event = fanotify_free_event, 255 }; 256