linux-kernel - Re: Fix OOPS in crash_kernel

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Message-ID: <87r5maqleh.wl%vmayatsk@redhat.com>
Date:	Tue, 20 Apr 2010 15:54:46 +0200
From:	Vitaly Mayatskikh <v.mayatskih@...il.com>
To:	Cong Wang <amwang@...hat.com>
Cc:	Vitaly Mayatskikh <v.mayatskih@...il.com>,
	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

At Tue, 20 Apr 2010 20:56:14 +0800, Cong Wang wrote:
> 
> 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?

Do it twice. start == end condition will work over and over, and
kernel will try to release_resource() again (and that's causes OOPS).

This scenario is unlikely to happen often (root privs, valid
crashkernel= in cmdline, dump-capture kernel not loaded), I hit it
only by chance.

-- 
wbr, Vitaly
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