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 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  20         /* dont merge two permission events */
  21         if ((old_fsn->mask & FAN_ALL_PERM_EVENTS) &&
  22             (new_fsn->mask & FAN_ALL_PERM_EVENTS))
  23                 return false;
  24 #endif
  25         pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
  26         old = FANOTIFY_E(old_fsn);
  27         new = FANOTIFY_E(new_fsn);
  28
  29         if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
  30             old->path.mnt == new->path.mnt &&
  31             old->path.dentry == new->path.dentry)
  32                 return true;
  33         return false;
  34 }
  35
  36 /* and the list better be locked by something too! */
  37 static struct fsnotify_event *fanotify_merge(struct list_head *list,
  38                                              struct fsnotify_event *event)
  39 {
  40         struct fsnotify_event *test_event;
  41         bool do_merge = false;
  42
  43         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
  44
  45         list_for_each_entry_reverse(test_event, list, list) {
  46                 if (should_merge(test_event, event)) {
  47                         do_merge = true;
  48                         break;
  49                 }
  50         }
  51
  52         if (!do_merge)
  53                 return NULL;
  54
  55         test_event->mask |= event->mask;
  56         return test_event;
  57 }
  58
  59 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  60 static int fanotify_get_response_from_access(struct fsnotify_group *group,
  61                                              struct fanotify_event_info *event)
  62 {
  63         int ret;
  64
  65         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  66
  67         wait_event(group->fanotify_data.access_waitq, event->response ||
  68                                 atomic_read(&group->fanotify_data.bypass_perm));
  69
  70         if (!event->response) /* bypass_perm set */
  71                 return 0;
  72
  73         /* userspace responded, convert to something usable */
  74         switch (event->response) {
  75         case FAN_ALLOW:
  76                 ret = 0;
  77                 break;
  78         case FAN_DENY:
  79         default:
  80                 ret = -EPERM;
  81         }
  82         event->response = 0;
  83
  84         pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
  85                  group, event, ret);
  86
  87         return ret;
  88 }
  89 #endif
  90
  91 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
  92                                        struct fsnotify_mark *vfsmnt_mark,
  93                                        u32 event_mask,
  94                                        void *data, int data_type)
  95 {
  96         __u32 marks_mask, marks_ignored_mask;
  97         struct path *path = data;
  98
  99         pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
 100                  " data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
 101                  event_mask, data, data_type);
 102
 103         /* if we don't have enough info to send an event to userspace say no */
 104         if (data_type != FSNOTIFY_EVENT_PATH)
 105                 return false;
 106
 107         /* sorry, fanotify only gives a damn about files and dirs */
 108         if (!S_ISREG(path->dentry->d_inode->i_mode) &&
 109             !S_ISDIR(path->dentry->d_inode->i_mode))
 110                 return false;
 111
 112         if (inode_mark && vfsmnt_mark) {
 113                 marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
 114                 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
 115         } else if (inode_mark) {
 116                 /*
 117                  * if the event is for a child and this inode doesn't care about
 118                  * events on the child, don't send it!
 119                  */
 120                 if ((event_mask & FS_EVENT_ON_CHILD) &&
 121                     !(inode_mark->mask & FS_EVENT_ON_CHILD))
 122                         return false;
 123                 marks_mask = inode_mark->mask;
 124                 marks_ignored_mask = inode_mark->ignored_mask;
 125         } else if (vfsmnt_mark) {
 126                 marks_mask = vfsmnt_mark->mask;
 127                 marks_ignored_mask = vfsmnt_mark->ignored_mask;
 128         } else {
 129                 BUG();
 130         }
 131
 132         if (S_ISDIR(path->dentry->d_inode->i_mode) &&
 133             (marks_ignored_mask & FS_ISDIR))
 134                 return false;
 135
 136         if (event_mask & marks_mask & ~marks_ignored_mask)
 137                 return true;
 138
 139         return false;
 140 }
 141
 142 static int fanotify_handle_event(struct fsnotify_group *group,
 143                                  struct inode *inode,
 144                                  struct fsnotify_mark *inode_mark,
 145                                  struct fsnotify_mark *fanotify_mark,
 146                                  u32 mask, void *data, int data_type,
 147                                  const unsigned char *file_name)
 148 {
 149         int ret = 0;
 150         struct fanotify_event_info *event;
 151         struct fsnotify_event *fsn_event;
 152         struct fsnotify_event *notify_fsn_event;
 153
 154         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 155         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 156         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 157         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 158         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 159         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 160         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 161         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 162         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 163         BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 164
 165         if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
 166                                         data_type))
 167                 return 0;
 168
 169         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
 170                  mask);
 171
 172         event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
 173         if (unlikely(!event))
 174                 return -ENOMEM;
 175
 176         fsn_event = &event->fse;
 177         fsnotify_init_event(fsn_event, inode, mask);
 178         event->tgid = get_pid(task_tgid(current));
 179         if (data_type == FSNOTIFY_EVENT_PATH) {
 180                 struct path *path = data;
 181                 event->path = *path;
 182                 path_get(&event->path);
 183         } else {
 184                 event->path.mnt = NULL;
 185                 event->path.dentry = NULL;
 186         }
 187 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 188         event->response = 0;
 189 #endif
 190
 191         notify_fsn_event = fsnotify_add_notify_event(group, fsn_event,
 192                                                      fanotify_merge);
 193         if (notify_fsn_event) {
 194                 /* Our event wasn't used in the end. Free it. */
 195                 fsnotify_destroy_event(group, fsn_event);
 196                 if (IS_ERR(notify_fsn_event))
 197                         return PTR_ERR(notify_fsn_event);
 198                 /* We need to ask about a different events after a merge... */
 199                 event = FANOTIFY_E(notify_fsn_event);
 200                 fsn_event = notify_fsn_event;
 201         }
 202
 203 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 204         if (fsn_event->mask & FAN_ALL_PERM_EVENTS)
 205                 ret = fanotify_get_response_from_access(group, event);
 206 #endif
 207         return ret;
 208 }
 209
 210 static void fanotify_free_group_priv(struct fsnotify_group *group)
 211 {
 212         struct user_struct *user;
 213
 214         user = group->fanotify_data.user;
 215         atomic_dec(&user->fanotify_listeners);
 216         free_uid(user);
 217 }
 218
 219 static void fanotify_free_event(struct fsnotify_event *fsn_event)
 220 {
 221         struct fanotify_event_info *event;
 222
 223         event = FANOTIFY_E(fsn_event);
 224         path_put(&event->path);
 225         put_pid(event->tgid);
 226         kmem_cache_free(fanotify_event_cachep, event);
 227 }
 228
 229 const struct fsnotify_ops fanotify_fsnotify_ops = {
 230         .handle_event = fanotify_handle_event,
 231         .free_group_priv = fanotify_free_group_priv,
 232         .free_event = fanotify_free_event,
 233 };