fs/notify/inotify/inotify_fsnotify.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * fs/inotify_user.c - inotify support for userspace
   4  *
   5  * Authors:
   6  *      John McCutchan  <ttb@tentacle.dhs.org>
   7  *      Robert Love     <rml@novell.com>
   8  *
   9  * Copyright (C) 2005 John McCutchan
  10  * Copyright 2006 Hewlett-Packard Development Company, L.P.
  11  *
  12  * Copyright (C) 2009 Eric Paris <Red Hat Inc>
  13  * inotify was largely rewriten to make use of the fsnotify infrastructure
  14  */
  15
  16 #include <linux/dcache.h> /* d_unlinked */
  17 #include <linux/fs.h> /* struct inode */
  18 #include <linux/fsnotify_backend.h>
  19 #include <linux/inotify.h>
  20 #include <linux/path.h> /* struct path */
  21 #include <linux/slab.h> /* kmem_* */
  22 #include <linux/types.h>
  23 #include <linux/sched.h>
  24 #include <linux/sched/user.h>
  25 #include <linux/sched/mm.h>
  26
  27 #include "inotify.h"
  28
  29 /*
  30  * Check if 2 events contain the same information.
  31  */
  32 static bool event_compare(struct fsnotify_event *old_fsn,
  33                           struct fsnotify_event *new_fsn)
  34 {
  35         struct inotify_event_info *old, *new;
  36
  37         old = INOTIFY_E(old_fsn);
  38         new = INOTIFY_E(new_fsn);
  39         if (old->mask & FS_IN_IGNORED)
  40                 return false;
  41         if ((old->mask == new->mask) &&
  42             (old->wd == new->wd) &&
  43             (old->name_len == new->name_len) &&
  44             (!old->name_len || !strcmp(old->name, new->name)))
  45                 return true;
  46         return false;
  47 }
  48
  49 static int inotify_merge(struct fsnotify_group *group,
  50                          struct fsnotify_event *event)
  51 {
  52         struct list_head *list = &group->notification_list;
  53         struct fsnotify_event *last_event;
  54
  55         last_event = list_entry(list->prev, struct fsnotify_event, list);
  56         return event_compare(last_event, event);
  57 }
  58
  59 int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
  60                                struct inode *inode, struct inode *dir,
  61                                const struct qstr *name, u32 cookie)
  62 {
  63         struct inotify_inode_mark *i_mark;
  64         struct inotify_event_info *event;
  65         struct fsnotify_event *fsn_event;
  66         struct fsnotify_group *group = inode_mark->group;
  67         int ret;
  68         int len = 0, wd;
  69         int alloc_len = sizeof(struct inotify_event_info);
  70         struct mem_cgroup *old_memcg;
  71
  72         if (name) {
  73                 len = name->len;
  74                 alloc_len += len + 1;
  75         }
  76
  77         pr_debug("%s: group=%p mark=%p mask=%x\n", __func__, group, inode_mark,
  78                  mask);
  79
  80         i_mark = container_of(inode_mark, struct inotify_inode_mark,
  81                               fsn_mark);
  82
  83         /*
  84          * We can be racing with mark being detached. Don't report event with
  85          * invalid wd.
  86          */
  87         wd = READ_ONCE(i_mark->wd);
  88         if (wd == -1)
  89                 return 0;
  90         /*
  91          * Whoever is interested in the event, pays for the allocation. Do not
  92          * trigger OOM killer in the target monitoring memcg as it may have
  93          * security repercussion.
  94          */
  95         old_memcg = set_active_memcg(group->memcg);
  96         event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
  97         set_active_memcg(old_memcg);
  98
  99         if (unlikely(!event)) {
 100                 /*
 101                  * Treat lost event due to ENOMEM the same way as queue
 102                  * overflow to let userspace know event was lost.
 103                  */
 104                 fsnotify_queue_overflow(group);
 105                 return -ENOMEM;
 106         }
 107
 108         /*
 109          * We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
 110          * for fanotify. inotify never reported IN_ISDIR with those events.
 111          * It looks like an oversight, but to avoid the risk of breaking
 112          * existing inotify programs, mask the flag out from those events.
 113          */
 114         if (mask & (IN_MOVE_SELF | IN_DELETE_SELF))
 115                 mask &= ~IN_ISDIR;
 116
 117         fsn_event = &event->fse;
 118         fsnotify_init_event(fsn_event);
 119         event->mask = mask;
 120         event->wd = wd;
 121         event->sync_cookie = cookie;
 122         event->name_len = len;
 123         if (len)
 124                 strcpy(event->name, name->name);
 125
 126         ret = fsnotify_add_event(group, fsn_event, inotify_merge);
 127         if (ret) {
 128                 /* Our event wasn't used in the end. Free it. */
 129                 fsnotify_destroy_event(group, fsn_event);
 130         }
 131
 132         if (inode_mark->flags & FSNOTIFY_MARK_FLAG_IN_ONESHOT)
 133                 fsnotify_destroy_mark(inode_mark, group);
 134
 135         return 0;
 136 }
 137
 138 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
 139 {
 140         inotify_ignored_and_remove_idr(fsn_mark, group);
 141 }
 142
 143 /*
 144  * This is NEVER supposed to be called.  Inotify marks should either have been
 145  * removed from the idr when the watch was removed or in the
 146  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 147  * torn down.  This is only called if the idr is about to be freed but there
 148  * are still marks in it.
 149  */
 150 static int idr_callback(int id, void *p, void *data)
 151 {
 152         struct fsnotify_mark *fsn_mark;
 153         struct inotify_inode_mark *i_mark;
 154         static bool warned = false;
 155
 156         if (warned)
 157                 return 0;
 158
 159         warned = true;
 160         fsn_mark = p;
 161         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 162
 163         WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
 164                 "idr.  Probably leaking memory\n", id, p, data);
 165
 166         /*
 167          * I'm taking the liberty of assuming that the mark in question is a
 168          * valid address and I'm dereferencing it.  This might help to figure
 169          * out why we got here and the panic is no worse than the original
 170          * BUG() that was here.
 171          */
 172         if (fsn_mark)
 173                 printk(KERN_WARNING "fsn_mark->group=%p wd=%d\n",
 174                         fsn_mark->group, i_mark->wd);
 175         return 0;
 176 }
 177
 178 static void inotify_free_group_priv(struct fsnotify_group *group)
 179 {
 180         /* ideally the idr is empty and we won't hit the BUG in the callback */
 181         idr_for_each(&group->inotify_data.idr, idr_callback, group);
 182         idr_destroy(&group->inotify_data.idr);
 183         if (group->inotify_data.ucounts)
 184                 dec_inotify_instances(group->inotify_data.ucounts);
 185 }
 186
 187 static void inotify_free_event(struct fsnotify_group *group,
 188                                struct fsnotify_event *fsn_event)
 189 {
 190         kfree(INOTIFY_E(fsn_event));
 191 }
 192
 193 /* ding dong the mark is dead */
 194 static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
 195 {
 196         struct inotify_inode_mark *i_mark;
 197
 198         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 199
 200         kmem_cache_free(inotify_inode_mark_cachep, i_mark);
 201 }
 202
 203 const struct fsnotify_ops inotify_fsnotify_ops = {
 204         .handle_inode_event = inotify_handle_inode_event,
 205         .free_group_priv = inotify_free_group_priv,
 206         .free_event = inotify_free_event,
 207         .freeing_mark = inotify_freeing_mark,
 208         .free_mark = inotify_free_mark,
 209 };