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_fsn->objectid == new_fsn->objectid) &&
  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 list_head *list,
  50                           struct fsnotify_event *event)
  51 {
  52         struct fsnotify_event *last_event;
  53
  54         last_event = list_entry(list->prev, struct fsnotify_event, list);
  55         return event_compare(last_event, event);
  56 }
  57
  58 int inotify_handle_event(struct fsnotify_group *group,
  59                          struct inode *inode,
  60                          u32 mask, const void *data, int data_type,
  61                          const struct qstr *file_name, u32 cookie,
  62                          struct fsnotify_iter_info *iter_info)
  63 {
  64         struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
  65         struct inotify_inode_mark *i_mark;
  66         struct inotify_event_info *event;
  67         struct fsnotify_event *fsn_event;
  68         int ret;
  69         int len = 0;
  70         int alloc_len = sizeof(struct inotify_event_info);
  71
  72         if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
  73                 return 0;
  74
  75         if ((inode_mark->mask & FS_EXCL_UNLINK) &&
  76             (data_type == FSNOTIFY_EVENT_PATH)) {
  77                 const struct path *path = data;
  78
  79                 if (d_unlinked(path->dentry))
  80                         return 0;
  81         }
  82         if (file_name) {
  83                 len = file_name->len;
  84                 alloc_len += len + 1;
  85         }
  86
  87         pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
  88                  mask);
  89
  90         i_mark = container_of(inode_mark, struct inotify_inode_mark,
  91                               fsn_mark);
  92
  93         /*
  94          * Whoever is interested in the event, pays for the allocation. Do not
  95          * trigger OOM killer in the target monitoring memcg as it may have
  96          * security repercussion.
  97          */
  98         memalloc_use_memcg(group->memcg);
  99         event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
 100         memalloc_unuse_memcg();
 101
 102         if (unlikely(!event)) {
 103                 /*
 104                  * Treat lost event due to ENOMEM the same way as queue
 105                  * overflow to let userspace know event was lost.
 106                  */
 107                 fsnotify_queue_overflow(group);
 108                 return -ENOMEM;
 109         }
 110
 111         /*
 112          * We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
 113          * for fanotify. inotify never reported IN_ISDIR with those events.
 114          * It looks like an oversight, but to avoid the risk of breaking
 115          * existing inotify programs, mask the flag out from those events.
 116          */
 117         if (mask & (IN_MOVE_SELF | IN_DELETE_SELF))
 118                 mask &= ~IN_ISDIR;
 119
 120         fsn_event = &event->fse;
 121         fsnotify_init_event(fsn_event, (unsigned long)inode);
 122         event->mask = mask;
 123         event->wd = i_mark->wd;
 124         event->sync_cookie = cookie;
 125         event->name_len = len;
 126         if (len)
 127                 strcpy(event->name, file_name->name);
 128
 129         ret = fsnotify_add_event(group, fsn_event, inotify_merge);
 130         if (ret) {
 131                 /* Our event wasn't used in the end. Free it. */
 132                 fsnotify_destroy_event(group, fsn_event);
 133         }
 134
 135         if (inode_mark->mask & IN_ONESHOT)
 136                 fsnotify_destroy_mark(inode_mark, group);
 137
 138         return 0;
 139 }
 140
 141 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
 142 {
 143         inotify_ignored_and_remove_idr(fsn_mark, group);
 144 }
 145
 146 /*
 147  * This is NEVER supposed to be called.  Inotify marks should either have been
 148  * removed from the idr when the watch was removed or in the
 149  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 150  * torn down.  This is only called if the idr is about to be freed but there
 151  * are still marks in it.
 152  */
 153 static int idr_callback(int id, void *p, void *data)
 154 {
 155         struct fsnotify_mark *fsn_mark;
 156         struct inotify_inode_mark *i_mark;
 157         static bool warned = false;
 158
 159         if (warned)
 160                 return 0;
 161
 162         warned = true;
 163         fsn_mark = p;
 164         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 165
 166         WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
 167                 "idr.  Probably leaking memory\n", id, p, data);
 168
 169         /*
 170          * I'm taking the liberty of assuming that the mark in question is a
 171          * valid address and I'm dereferencing it.  This might help to figure
 172          * out why we got here and the panic is no worse than the original
 173          * BUG() that was here.
 174          */
 175         if (fsn_mark)
 176                 printk(KERN_WARNING "fsn_mark->group=%p wd=%d\n",
 177                         fsn_mark->group, i_mark->wd);
 178         return 0;
 179 }
 180
 181 static void inotify_free_group_priv(struct fsnotify_group *group)
 182 {
 183         /* ideally the idr is empty and we won't hit the BUG in the callback */
 184         idr_for_each(&group->inotify_data.idr, idr_callback, group);
 185         idr_destroy(&group->inotify_data.idr);
 186         if (group->inotify_data.ucounts)
 187                 dec_inotify_instances(group->inotify_data.ucounts);
 188 }
 189
 190 static void inotify_free_event(struct fsnotify_event *fsn_event)
 191 {
 192         kfree(INOTIFY_E(fsn_event));
 193 }
 194
 195 /* ding dong the mark is dead */
 196 static void inotify_free_mark(struct fsnotify_mark *fsn_mark)
 197 {
 198         struct inotify_inode_mark *i_mark;
 199
 200         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 201
 202         kmem_cache_free(inotify_inode_mark_cachep, i_mark);
 203 }
 204
 205 const struct fsnotify_ops inotify_fsnotify_ops = {
 206         .handle_event = inotify_handle_event,
 207         .free_group_priv = inotify_free_group_priv,
 208         .free_event = inotify_free_event,
 209         .freeing_mark = inotify_freeing_mark,
 210         .free_mark = inotify_free_mark,
 211 };