Messages in this thread |  | | | From | Linus Torvalds <> | | Date | Thu, 17 Feb 2011 20:30:42 -0800 | | Subject | Re: BUG: Bad page map in process udevd (anon_vma: (null)) in 2.6.38-rc4 |
| |
On Thu, Feb 17, 2011 at 7:16 PM, Eric W. Biederman <ebiederm@xmission.com> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |