On Thu, Feb 17, 2011 at 7:16 PM, Eric W. Biederman
<ebiederm@xxxxxxxxxxxx> wrote:
>
> Interesting. I just got this with DEBUG_PAGEALLOC
> It looks like something in DEBUG_PAGEALLOC is interfering with taking a
> successful crashdump.
Hmm. I don't see why, but we don't care. Just the IP and the Code:
section is plenty good enough.
> 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.
Linus
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