linux-kernel - Re: [PATCH v2] firmware: dmi_scan: Fix ordering of product

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Date:	Fri, 17 Apr 2015 10:56:02 +0200
From:	Jean Delvare <jdelvare@...e.de>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Zhenzhong Duan <zhenzhong.duan@...cle.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Artem Savkov <artem.savkov@...il.com>,
	Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v2] firmware: dmi_scan: Fix ordering of product_uuid

On Fri, 17 Apr 2015 10:13:25 +0200, Jean Delvare wrote:
> In function dmi_present(), dmi_walk_early() calls dmi_table(), which
> calls dmi_decode(), which ultimately calls dmi_save_uuid(). This last
> function makes a decision based on the value of global variable
> dmi_ver. The problem is that this variable is set right _after_
> dmi_walk_early() returns. So dmi_save_uuid() always sees dmi_ver == 0
> regardless of the actual version implemented.
> 
> This causes /sys/class/dmi/id/product_uuid to always use the old
> ordering even on systems implementing DMI/SMBIOS 2.6 or later, which
> should use the new ordering.
> 
> This is broken since kernel v3.8 for legacy DMI implementations and
> since kernel v3.10 for SMBIOS 2 implementations. SMBIOS 3
> implementations with the 64-bit entry point are not affected.
> 
> The first breakage does not matter much as in practice legacy DMI
> implementations are always for versions older than 2.6, which is when
> the UUID ordering changed. The second breakage is more problematic as
> it affects the vast majority of x86 systems manufactured since 2009.
> 
> Signed-off-by: Jean Delvare <jdelvare@...e.de>
> Fixes: 9f9c9cbb6057 ("drivers/firmware/dmi_scan.c: fetch dmi version from SMBIOS if it exists")
> Fixes: 79bae42d51a5 ("dmi_scan: refactor dmi_scan_machine(), {smbios,dmi}_present()")
> Acked-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
> Cc: Ben Hutchings <ben@...adent.org.uk>
> Cc: Artem Savkov <artem.savkov@...il.com>
> Cc: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> Cc: Matt Fleming <matt.fleming@...el.com>
> Cc: stable@...r.kernel.org [v3.10+]
> ---
> Changes since v1:
>  * Rebased on torvalds/linux/master.

Bah, scratch that, I have come up with a different approach that will
make backporting this fix easier. Sorry for the noise.

-- 
Jean Delvare
SUSE L3 Support
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