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