linux-kernel - Re: [PATCH] EDAC, MCE, AMD: Fix code to prevent NULL dereference

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Message-ID: <20140218003654.GK4559@pd.tnic>
Date:	Tue, 18 Feb 2014 01:36:54 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
Cc:	dougthompson@...ssion.com, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] EDAC, MCE, AMD: Fix code to prevent NULL dereference

On Mon, Feb 17, 2014 at 04:36:24PM -0600, Aravind Gopalakrishnan wrote:
> snapshot of the oops from simulating on my system:
> [   28.846200] [Hardware Error]: MC0 Error:
> [   28.846218] BUG: unable to handle kernel NULL pointer dereference
> at           (null)
> [   28.846232] IP: [<ffffffff81608526>] amd_decode_mce+0x526/0x900

Ok, I see it now.

mce_amd_inj.c calls directly amd_decode_mce() which is wrong. What it
should do, instead, is what mce_log does:

	ret = atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
	...


and send the mce struct through the notifier chain so that if we haven't
registered on it, we don't decode the error.

> Shall I work up the patch with both sets of changes and resend?

Just replace the amd_decode_mce() call in mce_amd_inj.c with the above
call to the notifier and it should work, AFAICT. We should still add the
hunk I sent you earlier to take care of the module case. Oh, and make
amd_decode_mce() static so that nothing outside of mce_amd.c uses it.

I might be missing something but it is too late now and I'm going to bed
- more fun tomorrow :-)

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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