Pileus Git - ~andy/linux/blob - 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_group *group,
  92                                        struct inode *inode,
  93                                        struct fsnotify_mark *inode_mark,
  94                                        struct fsnotify_mark *vfsmnt_mark,
  95                                        __u32 event_mask, void *data, int data_type)
  96 {
  97         __u32 marks_mask, marks_ignored_mask;
  98         struct path *path = data;
  99
 100         pr_debug("%s: group=%p inode=%p inode_mark=%p vfsmnt_mark=%p "
 101                  "mask=%x data=%p data_type=%d\n", __func__, group, inode,
 102                  inode_mark, vfsmnt_mark, event_mask, data, data_type);
 103
 104         /* if we don't have enough info to send an event to userspace say no */
 105         if (data_type != FSNOTIFY_EVENT_PATH)
 106                 return false;
 107
 108         /* sorry, fanotify only gives a damn about files and dirs */
 109         if (!S_ISREG(path->dentry->d_inode->i_mode) &&
 110             !S_ISDIR(path->dentry->d_inode->i_mode))
 111                 return false;
 112
 113         if (inode_mark && vfsmnt_mark) {
 114                 marks_mask = (vfsmnt_mark->mask | inode_mark->mask);
 115                 marks_ignored_mask = (vfsmnt_mark->ignored_mask | inode_mark->ignored_mask);
 116         } else if (inode_mark) {
 117                 /*
 118                  * if the event is for a child and this inode doesn't care about
 119                  * events on the child, don't send it!
 120                  */
 121                 if ((event_mask & FS_EVENT_ON_CHILD) &&
 122                     !(inode_mark->mask & FS_EVENT_ON_CHILD))
 123                         return false;
 124                 marks_mask = inode_mark->mask;
 125                 marks_ignored_mask = inode_mark->ignored_mask;
 126         } else if (vfsmnt_mark) {
 127                 marks_mask = vfsmnt_mark->mask;
 128                 marks_ignored_mask = vfsmnt_mark->ignored_mask;
 129         } else {
 130                 BUG();
 131         }
 132
 133         if (S_ISDIR(path->dentry->d_inode->i_mode) &&
 134             (marks_ignored_mask & FS_ISDIR))
 135                 return false;
 136
 137         if (event_mask & marks_mask & ~marks_ignored_mask)
 138                 return true;
 139
 140         return false;
 141 }
 142
 143 static int fanotify_handle_event(struct fsnotify_group *group,
 144                                  struct inode *inode,
 145                                  struct fsnotify_mark *inode_mark,
 146                                  struct fsnotify_mark *fanotify_mark,
 147                                  u32 mask, void *data, int data_type,
 148                                  const unsigned char *file_name)
 149 {
 150         int ret = 0;
 151         struct fanotify_event_info *event;
 152         struct fsnotify_event *fsn_event;
 153         struct fsnotify_event *notify_fsn_event;
 154
 155         BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
 156         BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
 157         BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
 158         BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
 159         BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
 160         BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
 161         BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
 162         BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
 163         BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 164         BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 165
 166         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
 167                  mask);
 168
 169         event = kmem_cache_alloc(fanotify_event_cachep, GFP_KERNEL);
 170         if (unlikely(!event))
 171                 return -ENOMEM;
 172
 173         fsn_event = &event->fse;
 174         fsnotify_init_event(fsn_event, inode, mask);
 175         event->tgid = get_pid(task_tgid(current));
 176         if (data_type == FSNOTIFY_EVENT_PATH) {
 177                 struct path *path = data;
 178                 event->path = *path;
 179                 path_get(&event->path);
 180         } else {
 181                 event->path.mnt = NULL;
 182                 event->path.dentry = NULL;
 183         }
 184 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 185         event->response = 0;
 186 #endif
 187
 188         notify_fsn_event = fsnotify_add_notify_event(group, fsn_event,
 189                                                      fanotify_merge);
 190         if (notify_fsn_event) {
 191                 /* Our event wasn't used in the end. Free it. */
 192                 fsnotify_destroy_event(group, fsn_event);
 193                 if (IS_ERR(notify_fsn_event))
 194                         return PTR_ERR(notify_fsn_event);
 195                 /* We need to ask about a different events after a merge... */
 196                 event = FANOTIFY_E(notify_fsn_event);
 197                 fsn_event = notify_fsn_event;
 198         }
 199
 200 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 201         if (fsn_event->mask & FAN_ALL_PERM_EVENTS)
 202                 ret = fanotify_get_response_from_access(group, event);
 203 #endif
 204         return ret;
 205 }
 206
 207 static void fanotify_free_group_priv(struct fsnotify_group *group)
 208 {
 209         struct user_struct *user;
 210
 211         user = group->fanotify_data.user;
 212         atomic_dec(&user->fanotify_listeners);
 213         free_uid(user);
 214 }
 215
 216 static void fanotify_free_event(struct fsnotify_event *fsn_event)
 217 {
 218         struct fanotify_event_info *event;
 219
 220         event = FANOTIFY_E(fsn_event);
 221         path_put(&event->path);
 222         put_pid(event->tgid);
 223         kmem_cache_free(fanotify_event_cachep, event);
 224 }
 225
 226 const struct fsnotify_ops fanotify_fsnotify_ops = {
 227         .handle_event = fanotify_handle_event,
 228         .should_send_event = fanotify_should_send_event,
 229         .free_group_priv = fanotify_free_group_priv,
 230         .free_event = fanotify_free_event,
 231         .freeing_mark = NULL,
 232 };