linux-kernel - Re: v2.6.31-rc6: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008

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Message-ID: <a8e1da0908200119u83c965bgf08996b0aa4aca52@mail.gmail.com>
Date:	Thu, 20 Aug 2009 16:19:08 +0800
From:	Dave Young <hidave.darkstar@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: v2.6.31-rc6: BUG: unable to handle kernel NULL pointer 
	dereference at 0000000000000008

On Thu, Aug 20, 2009 at 4:00 PM, Eric W. Biederman<ebiederm@...ssion.com> wrote:
> Dave Young <hidave.darkstar@...il.com> writes:
>
>> On Thu, Aug 20, 2009 at 2:07 PM, Eric W. Biederman<ebiederm@...ssion.com> wrote:
>>>
>>> ebiederm@...ssion.com (Eric W. Biederman) writes:
>>>
>>>> I'm not certain who I should route this too, but I just had 2.6.31-rc6
>>>> fall over on me.  I don't know how reproducible this will be but
>>>> I have a full crash dump if someone is interested in looking into this.
>>>
>>> Looks like I was wrong.  This is appears trivial to reproduce,
>>> I have just reproduced it two more times in a row.  I think
>>> the problem is pty related.
>>>
>>> I was looking into a change in behavior on 2.6.31-rc6 where
>>> data was being lost, and it appears one variant of my test program
>>> kills the kernel.
>>>
>>> The following program run as an unprivileged user causes a kernel
>>> panic in about a minute:
>>>
>>> aka
>>>
>>> while :; do ./KernelTtyTest ; done
>>
>> The test app failed for me:
>>
>> read failed: Input/output error
>> lastbytes: '\r\nprocess_cmd read failed: Interrupted system
>> call\r\necho _2_\r\n'
>> Aborted
>
>
> Oh.  It definitely fails.  I just found that when it failed
> about 600 times in a row it took my kernel with it.  I was
> developing it to understand tty interactions, and when I realized
> that the version I had was killing my kernel I sent it out
> as it was a nice self contained test case.

Confirm: I can reproduce on i386 machine.

>
> Eric
>



-- 
Regards
dave
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