linux-kernel - [PATCH 4.16 046/272] firmware: dmi_scan: Fix UUID length safety check

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Date:   Mon, 28 May 2018 12:01:19 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jean Delvare <jdelvare@...e.de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.16 046/272] firmware: dmi_scan: Fix UUID length safety check

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jean Delvare <jdelvare@...e.de>

[ Upstream commit 90fe6f8ff00a07641ca893d64f75ca22ce77cca2 ]

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")
Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/firmware/dmi_scan.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -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;