fs/notify/fanotify/fanotify.c

   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 (!d_is_reg(path->dentry) &&
 119             !d_can_lookup(path->dentry))
 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 (d_is_dir(path->dentry) &&
 143             !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
 144                 return false;
 145
 146         if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
 147                                  ~marks_ignored_mask)
 148                 return true;
 149
 150         return false;
 151 }
 152
 153 struct fanotify_event_info *fanotify_alloc_event(struct inode *inode, u32 mask,
 154                                                  struct path *path)
 155 {
 156         struct fanotify_event_info *event;
 157
 158 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 159         if (mask & FAN_ALL_PERM_EVENTS) {
 160                 struct fanotify_perm_event_info *pevent;
 161
 162                 pevent = kmem_cache_alloc(fanotify_perm_event_cachep,
 163                                           GFP_KERNEL);
 164                 if (!pevent)
 165                         return NULL;
 166                 event = &pevent->fae;
 167                 pevent->response = 0;
 168                 goto init;
 169         }
 170 #endif
 171         event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
 172         if (!event)
 173                 return NULL;
 174 init: __maybe_unused
 175         fsnotify_init_event(&event->fse, inode, mask);
 176         event->tgid = get_pid(task_tgid(current));
 177         if (path) {
 178                 event->path = *path;
 179                 path_get(&event->path);
 180         } else {
 181                 event->path.mnt = NULL;
 182                 event->path.dentry = NULL;
 183         }
 184         return event;
 185 }
 186
 187 static int fanotify_handle_event(struct fsnotify_group *group,
 188                                  struct inode *inode,
 189                                  struct fsnotify_mark *inode_mark,
 190                                  struct fsnotify_mark *fanotify_mark,
 191                                  u32 mask, void *data, int data_type,
 192                                  const unsigned char *file_name, u32 cookie)
 193 {
 194         int ret = 0;
 195         struct fanotify_event_info *event;
 196         struct fsnotify_event *fsn_event;
 197
 198         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 199         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 200         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 201         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 202         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 203         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 204         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 205         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 206         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 207         BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 208
 209         if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
 210                                         data_type))
 211                 return 0;
 212
 213         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
 214                  mask);
 215
 216         event = fanotify_alloc_event(inode, mask, data);
 217         if (unlikely(!event))
 218                 return -ENOMEM;
 219
 220         fsn_event = &event->fse;
 221         ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
 222         if (ret) {
 223                 /* Permission events shouldn't be merged */
 224                 BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
 225                 /* Our event wasn't used in the end. Free it. */
 226                 fsnotify_destroy_event(group, fsn_event);
 227
 228                 return 0;
 229         }
 230
 231 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 232         if (mask & FAN_ALL_PERM_EVENTS) {
 233                 ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event));
 234                 fsnotify_destroy_event(group, fsn_event);
 235         }
 236 #endif
 237         return ret;
 238 }
 239
 240 static void fanotify_free_group_priv(struct fsnotify_group *group)
 241 {
 242         struct user_struct *user;
 243
 244         user = group->fanotify_data.user;
 245         atomic_dec(&user->fanotify_listeners);
 246         free_uid(user);
 247 }
 248
 249 static void fanotify_free_event(struct fsnotify_event *fsn_event)
 250 {
 251         struct fanotify_event_info *event;
 252
 253         event = FANOTIFY_E(fsn_event);
 254         path_put(&event->path);
 255         put_pid(event->tgid);
 256 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 257         if (fsn_event->mask & FAN_ALL_PERM_EVENTS) {
 258                 kmem_cache_free(fanotify_perm_event_cachep,
 259                                 FANOTIFY_PE(fsn_event));
 260                 return;
 261         }
 262 #endif
 263         kmem_cache_free(fanotify_event_cachep, event);
 264 }
 265
 266 const struct fsnotify_ops fanotify_fsnotify_ops = {
 267         .handle_event = fanotify_handle_event,
 268         .free_group_priv = fanotify_free_group_priv,
 269         .free_event = fanotify_free_event,
 270 };