linux-kernel - Re: [kallsyms] general protection fault: 0000 [#1] PREEMPT DEBUG

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Date:	Mon, 11 Nov 2013 08:27:09 -0500
From:	Joe Mario <jmario@...hat.com>
To:	Michal Marek <mmarek@...e.cz>
CC:	Andi Kleen <andi@...stfloor.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [kallsyms] general protection fault: 0000 [#1] PREEMPT DEBUG_PAGEALLOC

On 11/11/2013 07:07 AM, Michal Marek wrote:
> On 10.11.2013 16:23, Andi Kleen wrote:
>> On Sun, Nov 10, 2013 at 05:40:05PM +0800, Fengguang Wu wrote:
>>> Hi Joe,
>>>
>>> FYI. Here is another bisect result.
>>
>> I bet it's that strncpy() in kallsyms.c and someone passing in a too
>> short buffer on a 32bit kernel.
>>
>> We should really kill strncpy(), it's just evil.
>
> I'm testing a patch for include/linux/pci.h to use line numbers instead
> of the PCI ID macros to declare the __pci_fixup_* symbols. If that
> works, we can revert the limit back to 128 and only keep the check in
> kallsyms.c.
>
> Michal

Michal:
  That would be great.

  I found six locations which were still using an array size hardwired to "128" instead of KSYM_NAME_LEN.  But none of them were related to the crash Fengguang Wu reported.  We built a 32-bit kernel from his config (with a few issues) but were unable to reproduce the crash.  Still trying.

  Whatever happens, I agree the check in kallsyms.c for kernel symbols whose length exceeds the buffer size, needs to be in place.

Joe

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