linux-kernel - Re: BUG: Bad page map in process udevd (anon

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Date:	Fri, 18 Feb 2011 07:25:20 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	torvalds@...ux-foundation.org, ebiederm@...ssion.com,
	opurdila@...acom.com, mingo@...e.hu, mhocko@...e.cz,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: BUG: Bad page map in process udevd (anon_vma: (null)) in
 2.6.38-rc4

Le jeudi 17 février 2011 à 20:36 -0800, David Miller a écrit :
> From: Linus Torvalds <torvalds@...ux-foundation.org>
> Date: Thu, 17 Feb 2011 20:30:42 -0800
> 
> > On Thu, Feb 17, 2011 at 7:16 PM, Eric W. Biederman
> > <ebiederm@...ssion.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!

I believe we can apply Linus patch as is for current linux-2.6

Then add a second patch for previous kernels (the parts I added), since
we might had a previous bug, un-noticed ?



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