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