linux/fs/notify/inotify/inotify.h
Eric Paris 528da3e9e2 inotify: inotify_destroy_mark_entry could get called twice
inotify_destroy_mark_entry could get called twice for the same mark since it
is called directly in inotify_rm_watch and when the mark is being destroyed for
another reason.  As an example assume that the file being watched was just
deleted so inotify_destroy_mark_entry would get called from the path
fsnotify_inoderemove() -> fsnotify_destroy_marks_by_inode() ->
fsnotify_destroy_mark_entry() -> inotify_destroy_mark_entry().  If this
happened at the same time as userspace tried to remove a watch via
inotify_rm_watch we could attempt to remove the mark from the idr twice and
could thus double dec the ref cnt and potentially could be in a use after
free/double free situation.  The fix is to have inotify_rm_watch use the
generic recursive safe fsnotify_destroy_mark_by_entry() so we are sure the
inotify_destroy_mark_entry() function can only be called one.

This patch also renames the function to inotify_ingored_remove_idr() so it is
clear what is actually going on in the function.

Hopefully this fixes:
[   20.342058] idr_remove called for id=20 which is not allocated.
[   20.348000] Pid: 1860, comm: udevd Not tainted 2.6.30-tip #1077
[   20.353933] Call Trace:
[   20.356410]  [<ffffffff811a82b7>] idr_remove+0x115/0x18f
[   20.361737]  [<ffffffff8134259d>] ? _spin_lock+0x6d/0x75
[   20.367061]  [<ffffffff8111640a>] ? inotify_destroy_mark_entry+0xa3/0xcf
[   20.373771]  [<ffffffff8111641e>] inotify_destroy_mark_entry+0xb7/0xcf
[   20.380306]  [<ffffffff81115913>] inotify_freeing_mark+0xe/0x10
[   20.386238]  [<ffffffff8111410d>] fsnotify_destroy_mark_by_entry+0x143/0x170
[   20.393293]  [<ffffffff811163a3>] inotify_destroy_mark_entry+0x3c/0xcf
[   20.399829]  [<ffffffff811164d1>] sys_inotify_rm_watch+0x9b/0xc6
[   20.405850]  [<ffffffff8100bcdb>] system_call_fastpath+0x16/0x1b

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Eric Paris <eparis@redhat.com>
Tested-by: Peter Ziljlstra <peterz@infradead.org>
2009-06-19 12:42:48 -04:00

23 lines
664 B
C

#include <linux/fsnotify_backend.h>
#include <linux/inotify.h>
#include <linux/slab.h> /* struct kmem_cache */
extern struct kmem_cache *event_priv_cachep;
struct inotify_event_private_data {
struct fsnotify_event_private_data fsnotify_event_priv_data;
int wd;
};
struct inotify_inode_mark_entry {
/* fsnotify_mark_entry MUST be the first thing */
struct fsnotify_mark_entry fsn_entry;
int wd;
};
extern void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry *entry,
struct fsnotify_group *group);
extern void inotify_free_event_priv(struct fsnotify_event_private_data *event_priv);
extern const struct fsnotify_ops inotify_fsnotify_ops;