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SubjectRe: BUG: Bad page map in process udevd (anon_vma: (null)) in 2.6.38-rc4
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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 17 Feb 2011 20:30:42 -0800

> On Thu, Feb 17, 2011 at 7:16 PM, Eric W. Biederman
> <ebiederm@xmission.com> wrote:
>> BUG: unable to handle kernel paging request at ffff8801adf8d760
>> IP: [<ffffffff8140c7ca>] unregister_netdevice_queue+0x3a/0xb0
>
> Yup. That's the "list_move()". The disassembly is exactly what I'd
> expect from __list_del():
>
> 16: 48 8b 93 a0 00 00 00 mov 0xa0(%rbx),%rdx
> 1d: 48 8b 83 a8 00 00 00 mov 0xa8(%rbx),%rax
> 24: 48 8d bb a0 00 00 00 lea 0xa0(%rbx),%rdi
> 2b:* 48 89 42 08 mov %rax,0x8(%rdx) <-- trapping instruction
> 2f: 48 89 10 mov %rdx,(%rax)
>
> So I think we can consider this confirmed: it really is the stale
> queue left over on the stack (introduced by commit 443457242beb). With
> CONFIG_DEBUG_PAGEALLOC, you get a page fault when it tries to update
> the now stale pointers.
>
> The patch from Eric Dumazet (which adds a few more cases to my patch
> and hopefully catches them all) almost certainly fixes this rather
> nasty memory corruption.

Eric D., please get a final version of the fix posted to netdev and
I'll make sure it slithers it's way to Linus's tree :-)

Thanks!


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