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