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
  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 };