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 struct fsnotify_event *fanotify_merge(struct list_head *list,
  32                                              struct fsnotify_event *event)
  33 {
  34         struct fsnotify_event *test_event;
  35         bool do_merge = false;
  36
  37         pr_debug("%s: list=%p event=%p\n", __func__, list, event);
  38
  39 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  40         /*
  41          * Don't merge a permission event with any other event so that we know
  42          * the event structure we have created in fanotify_handle_event() is the
  43          * one we should check for permission response.
  44          */
  45         if (event->mask & FAN_ALL_PERM_EVENTS)
  46                 return NULL;
  47 #endif
  48
  49         list_for_each_entry_reverse(test_event, list, list) {
  50                 if (should_merge(test_event, event)) {
  51                         do_merge = true;
  52                         break;
  53                 }
  54         }
  55
  56         if (!do_merge)
  57                 return NULL;
  58
  59         test_event->mask |= event->mask;
  60         return test_event;
  61 }
  62
  63 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  64 static int fanotify_get_response_from_access(struct fsnotify_group *group,
  65                                              struct fanotify_event_info *event)
  66 {
  67         int ret;
  68
  69         pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  70
  71         wait_event(group->fanotify_data.access_waitq, event->response ||
  72                                 atomic_read(&group->fanotify_data.bypass_perm));
  73
  74         if (!event->response) /* bypass_perm set */
  75                 return 0;
  76
  77         /* userspace responded, convert to something usable */
  78         switch (event->response) {
  79         case FAN_ALLOW:
  80                 ret = 0;
  81                 break;
  82         case FAN_DENY:
  83         default:
  84                 ret = -EPERM;
  85         }
  86         event->response = 0;
  87
  88         pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
  89                  group, event, ret);
  90
  91         return ret;
  92 }
  93 #endif
  94
  95 static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
  96                                        struct fsnotify_mark *vfsmnt_mark,
  97                                        u32 event_mask,
  98                                        void *data, int data_type)
  99 {
 100         __u32 marks_mask, marks_ignored_mask;
 101         struct path *path = data;
 102
 103         pr_debug("%s: inode_mark=%p vfsmnt_mark=%p mask=%x data=%p"
 104                  " data_type=%d\n", __func__, inode_mark, vfsmnt_mark,
 105                  event_mask, data, data_type);
 106
 107         /* if we don't have enough info to send an event to userspace say no */
 108         if (data_type != FSNOTIFY_EVENT_PATH)
 109                 return false;
 110
 111         /* sorry, fanotify only gives a damn about files and dirs */
 112         if (!S_ISREG(path->dentry->d_inode->i_mode) &&
 113             !S_ISDIR(path->dentry->d_inode->i_mode))
 114                 return false;
 115
 116         if (inode_mark && vfsmnt_mark) {
 117                 marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
 118                 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
 119         } else if (inode_mark) {
 120                 /*
 121                  * if the event is for a child and this inode doesn't care about
 122                  * events on the child, don't send it!
 123                  */
 124                 if ((event_mask & FS_EVENT_ON_CHILD) &&
 125                     !(inode_mark->mask & FS_EVENT_ON_CHILD))
 126                         return false;
 127                 marks_mask = inode_mark->mask;
 128                 marks_ignored_mask = inode_mark->ignored_mask;
 129         } else if (vfsmnt_mark) {
 130                 marks_mask = vfsmnt_mark->mask;
 131                 marks_ignored_mask = vfsmnt_mark->ignored_mask;
 132         } else {
 133                 BUG();
 134         }
 135
 136         if (S_ISDIR(path->dentry->d_inode->i_mode) &&
 137             (marks_ignored_mask & FS_ISDIR))
 138                 return false;
 139
 140         if (event_mask & marks_mask & ~marks_ignored_mask)
 141                 return true;
 142
 143         return false;
 144 }
 145
 146 static int fanotify_handle_event(struct fsnotify_group *group,
 147                                  struct inode *inode,
 148                                  struct fsnotify_mark *inode_mark,
 149                                  struct fsnotify_mark *fanotify_mark,
 150                                  u32 mask, void *data, int data_type,
 151                                  const unsigned char *file_name)
 152 {
 153         int ret = 0;
 154         struct fanotify_event_info *event;
 155         struct fsnotify_event *fsn_event;
 156         struct fsnotify_event *notify_fsn_event;
 157
 158         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 159         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 160         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 161         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 162         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 163         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 164         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 165         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 166         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 167         BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 168
 169         if (!fanotify_should_send_event(inode_mark, fanotify_mark, mask, data,
 170                                         data_type))
 171                 return 0;
 172
 173         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
 174                  mask);
 175
 176         event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
 177         if (unlikely(!event))
 178                 return -ENOMEM;
 179
 180         fsn_event = &event->fse;
 181         fsnotify_init_event(fsn_event, inode, mask);
 182         event->tgid = get_pid(task_tgid(current));
 183         if (data_type == FSNOTIFY_EVENT_PATH) {
 184                 struct path *path = data;
 185                 event->path = *path;
 186                 path_get(&event->path);
 187         } else {
 188                 event->path.mnt = NULL;
 189                 event->path.dentry = NULL;
 190         }
 191 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 192         event->response = 0;
 193 #endif
 194
 195         notify_fsn_event = fsnotify_add_notify_event(group, fsn_event,
 196                                                      fanotify_merge);
 197         if (notify_fsn_event) {
 198                 /* Our event wasn't used in the end. Free it. */
 199                 fsnotify_destroy_event(group, fsn_event);
 200                 if (IS_ERR(notify_fsn_event))
 201                         return PTR_ERR(notify_fsn_event);
 202         }
 203
 204 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 205         if (mask & FAN_ALL_PERM_EVENTS)
 206                 ret = fanotify_get_response_from_access(group, event);
 207 #endif
 208         return ret;
 209 }
 210
 211 static void fanotify_free_group_priv(struct fsnotify_group *group)
 212 {
 213         struct user_struct *user;
 214
 215         user = group->fanotify_data.user;
 216         atomic_dec(&user->fanotify_listeners);
 217         free_uid(user);
 218 }
 219
 220 static void fanotify_free_event(struct fsnotify_event *fsn_event)
 221 {
 222         struct fanotify_event_info *event;
 223
 224         event = FANOTIFY_E(fsn_event);
 225         path_put(&event->path);
 226         put_pid(event->tgid);
 227         kmem_cache_free(fanotify_event_cachep, event);
 228 }
 229
 230 const struct fsnotify_ops fanotify_fsnotify_ops = {
 231         .handle_event = fanotify_handle_event,
 232         .free_group_priv = fanotify_free_group_priv,
 233         .free_event = fanotify_free_event,
 234 };