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

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Date:	Thu, 20 Aug 2009 01:00:06 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Dave Young <hidave.darkstar@...il.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

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.

Eric
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