[PATCH v2] firmware: dmi_scan: Fix ordering of product_uuid

[PATCH v2] firmware: dmi_scan: Fix ordering of product_uuid

[Jean Delvare]

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@suse.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@oracle.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Artem Savkov <artem.savkov@gmail.com>
Cc: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: stable@vger.kernel.org [v3.10+]
---
Changes since v1:
 * Rebased on torvalds/linux/master.

 drivers/firmware/dmi_scan.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- linux-4.0.orig/drivers/firmware/dmi_scan.c	2015-04-13 00:12:50.000000000 +0200
+++ linux-4.0/drivers/firmware/dmi_scan.c	2015-04-15 10:24:37.556994240 +0200
@@ -499,19 +499,20 @@ static int __init dmi_present(const u8 *
 	buf += 16;
 
 	if (memcmp(buf, "_DMI_", 5) == 0 && dmi_checksum(buf, 15)) {
+		if (smbios_ver)
+			dmi_ver = smbios_ver;
+		else
+			dmi_ver = (buf[14] & 0xF0) << 4 | (buf[14] & 0x0F);
 		dmi_num = get_unaligned_le16(buf + 12);
 		dmi_len = get_unaligned_le16(buf + 6);
 		dmi_base = get_unaligned_le32(buf + 8);
 
 		if (dmi_walk_early(dmi_decode) == 0) {
 			if (smbios_ver) {
-				dmi_ver = smbios_ver;
 				pr_info("SMBIOS %d.%d%s present.\n",
 				       dmi_ver >> 8, dmi_ver & 0xFF,
 				       (dmi_ver < 0x0300) ? "" : ".x");
 			} else {
-				dmi_ver = (buf[14] & 0xF0) << 4 |
-					   (buf[14] & 0x0F);
 				pr_info("Legacy DMI %d.%d present.\n",
 				       dmi_ver >> 8, dmi_ver & 0xFF);
 			}


-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH v2] firmware: dmi_scan: Fix ordering of product_uuid

[Jean Delvare]

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@suse.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@oracle.com>
> Cc: Ben Hutchings <ben@decadent.org.uk>
> Cc: Artem Savkov <artem.savkov@gmail.com>
> Cc: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
> Cc: Matt Fleming <matt.fleming@intel.com>
> Cc: stable@vger.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