[<ffffffff>] 0xffffffff
>
> -> #0 (&bb->mutex){--..}:
>        [<c017d8b7>] validate_chain+0x6b7/0xf50
>        [<c017ef2b>] __lock_acquire+0x2cb/0x5b0
>        [<c017f299>] lock_acquire+0x89/0xc0
>        [<c0d6f2ab>] __mutex_lock_common+0xab/0x3c0
>        [<c0d6f698>] mutex_lock_nested+0x38/0x50
>        [<c020ba20>] mmap+0x40/0xa0
>        [<c01b111e>] mmap_region+0x14e/0x450
>        [<c01b170f>] do_mmap_pgoff+0x2ef/0x310
>        [<c0125a3d>] sys_mmap2+0xad/0xc0
>        [<c012146f>] sysenter_do_call+0x12/0x43
>        [<ffffffff>] 0xffffffff
>
> other info that might help us debug this:
>
> 1 lock held by X/4873:
>  #0:  (&mm->mmap_sem){----}, at: [<c0125a1e>] sys_mmap2+0x8e/0xc0
>
> stack backtrace:
> Pid: 4873, comm: X Not tainted 2.6.27-rc6-tip #1
>  [<c017cd09>] print_circular_bug_tail+0x79/0xc0
>  [<c017d8b7>] validate_chain+0x6b7/0xf50
>  [<c017a5b5>] ? trace_hardirqs_off_caller+0x15/0xb0
>  [<c017ef2b>] __lock_acquire+0x2cb/0x5b0
>  [<c017f299>] lock_acquire+0x89/0xc0
>  [<c020ba20>] ? mmap+0x40/0xa0
>  [<c0d6f2ab>] __mutex_lock_common+0xab/0x3c0
>  [<c020ba20>] ? mmap+0x40/0xa0
>  [<c0d6f698>] mutex_lock_nested+0x38/0x50
>  [<c020ba20>] ? mmap+0x40/0xa0
>  [<c020ba20>] mmap+0x40/0xa0
>  [<c01b111e>] mmap_region+0x14e/0x450
>  [<c01afb88>] ? arch_get_unmapped_area_topdown+0xf8/0x160
>  [<c01b170f>] do_mmap_pgoff+0x2ef/0x310
>  [<c0125a3d>] sys_mmap2+0xad/0xc0
>  [<c012146f>] sysenter_do_call+0x12/0x43
>  [<c0120000>] ? __switch_to+0x130/0x220
>  =======================
> evbug.c: Event. Dev: input3, Type: 20, Code: 0, Value: 500
> warning: `sudo' uses deprecated v2 capabilities in a way that may be insecure.
>
> i've attached the config.
>
> at first sight it looks like a genuine bug in fs/sysfs/bin.c?

Yes, it is a real bug by the looks. bin.c takes bb->mutex under mmap_sem
when it is mmapped, and then does its copy_*_user under bb->mutex too.

Here is a basic fix for the sysfs lor.


From: Nick Piggin <npiggin@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>