Messages in this thread | | | Subject | Re: [PATCH] inotify: inotify_destroy_mark_entry could get called twice | From | Peter Zijlstra <> | Date | Thu, 18 Jun 2009 13:25:18 +0200 |
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On Fri, 2009-06-12 at 16:26 -0400, Eric Paris wrote: > 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>
Tested-by: Peter Zijlstra <peterz@infradead.org>
Thanks Eric!!
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