linux-kernel - Re: Fix OOPS in crash_kernel

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Message-ID: <4BCDA46E.9030405@redhat.com>
Date:	Tue, 20 Apr 2010 20:56:14 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Vitaly Mayatskikh <v.mayatskih@...il.com>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Neil Horman <nhorman@...driver.com>
Subject: Re: Fix OOPS in crash_kernel_shrink

Vitaly Mayatskikh wrote:
> Two "echo 0 > /sys/kernel/kexec_crash_size" OOPSes kernel. Also
> content of this file is invalid after first shrink to zero: it shows 1
> instead of 0.
> 
> This patch fixes it.

Hmmm, I certainly did tests for 'echo 0 > kexec_crash_size' when I
worked on this, but I didn't get any oops. Can you show me the full
oops?

But yes, the size calculation looks wrong.

> 
> Signed-off-by: Vitaly Mayatskikh <v.mayatskih@...il.com>
> 
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 87ebe8a..474a847 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -1134,11 +1134,9 @@ int crash_shrink_memory(unsigned long new_size)
>  
>  	free_reserved_phys_range(end, crashk_res.end);
>  
> -	if (start == end) {
> -		crashk_res.end = end;
> +	if (start == end)
>  		release_resource(&crashk_res);
> -	} else
> -		crashk_res.end = end - 1;
> +	crashk_res.end = end - 1;
>  

If we do this, crashk_res.end will be ahead of crashk.start.

Thanks.
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