linux-kernel - [PATCH] firmware: dmi_scan: Fix UUID length safety check

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Message-ID: <20180409145143.4daa1706@endymion>
Date:   Mon, 9 Apr 2018 14:51:43 +0200
From:   Jean Delvare <jdelvare@...e.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH] firmware: dmi_scan: Fix UUID length safety check

The test which ensures that the DMI type 1 structure is long enough
to hold the UUID is off by one. It would fail if the structure is
exactly 24 bytes long, while that's sufficient to hold the UUID.

I don't expect this bug to cause problem in practice because all
implementations I have seen had length 8, 25 or 27 bytes, in line
with the SMBIOS specifications. But let's fix it still.

Signed-off-by: Jean Delvare <jdelvare@...e.de>
Fixes: a814c3597a6b ("firmware: dmi_scan: Check DMI structure length")
Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>
---
 drivers/firmware/dmi_scan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-4.16.orig/drivers/firmware/dmi_scan.c	2018-04-08 09:32:20.508719012 +0200
+++ linux-4.16/drivers/firmware/dmi_scan.c	2018-04-09 11:24:57.937044642 +0200
@@ -186,7 +186,7 @@ static void __init dmi_save_uuid(const s
 	char *s;
 	int is_ff = 1, is_00 = 1, i;
 
-	if (dmi_ident[slot] || dm->length <= index + 16)
+	if (dmi_ident[slot] || dm->length < index + 16)
 		return;
 
 	d = (u8 *) dm + index;


-- 
Jean Delvare
SUSE L3 Support