[PATCH v2] firmware: dmi_scan: Only honor end-of-table for 64-bit tables

[PATCH v2] firmware: dmi_scan: Only honor end-of-table for 64-bit tables

[Jean Delvare]

A 32-bit entry point to a DMI table says how many structures the table
contains. The SMBIOS specification explicitly says that end-of-table
markers should be ignored if they are not actually at the end of the
DMI table. So only honor the end-of-table marker for tables accessed
through 64-bit entry points, as they do not specify a structure count.

Fixes: fc43026278 ("dmi: add support for SMBIOS 3.0 64-bit entry point")
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
Changes since v1:
 * Added comments to explain the logic of the code.

 drivers/firmware/dmi_scan.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- linux-4.1-rc1.orig/drivers/firmware/dmi_scan.c	2015-04-30 15:52:43.304650745 +0200
+++ linux-4.1-rc1/drivers/firmware/dmi_scan.c	2015-04-30 16:16:46.898136915 +0200
@@ -89,9 +89,9 @@ static void dmi_table(u8 *buf,
 
 	/*
 	 * Stop when we have seen all the items the table claimed to have
-	 * (SMBIOS < 3.0 only) OR we reach an end-of-table marker OR we run
-	 * off the end of the table (should never happen but sometimes does
-	 * on bogus implementations.)
+	 * (SMBIOS < 3.0 only) OR we reach an end-of-table marker (SMBIOS
+	 * >= 3.0 only) OR we run off the end of the table (should never
+	 * happen but sometimes does on bogus implementations.)
 	 */
 	while ((!dmi_num || i < dmi_num) &&
 	       (data - buf + sizeof(struct dmi_header)) <= dmi_len) {
@@ -110,8 +110,13 @@ static void dmi_table(u8 *buf,
 
 		/*
 		 * 7.45 End-of-Table (Type 127) [SMBIOS reference spec v3.0.0]
+		 * For tables behind a 64-bit entry point, we have no item
+		 * count and no exact table length, so stop on end-of-table
+		 * marker. For tables behind a 32-bit entry point, we have
+		 * seen OEM structures behind the end-of-table marker on
+		 * some systems, so don't trust it.
 		 */
-		if (dm->type == DMI_ENTRY_END_OF_TABLE)
+		if (!dmi_num && dm->type == DMI_ENTRY_END_OF_TABLE)
 			break;
 
 		data += 2;


-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH v2] firmware: dmi_scan: Only honor end-of-table for 64-bit tables

[Ard Biesheuvel]

On 30 April 2015 at 16:23, Jean Delvare <jdelvare@suse.de> wrote:
> A 32-bit entry point to a DMI table says how many structures the table
> contains. The SMBIOS specification explicitly says that end-of-table
> markers should be ignored if they are not actually at the end of the
> DMI table. So only honor the end-of-table marker for tables accessed
> through 64-bit entry points, as they do not specify a structure count.
>
> Fixes: fc43026278 ("dmi: add support for SMBIOS 3.0 64-bit entry point")
> Signed-off-by: Jean Delvare <jdelvare@suse.de>
> Cc: Leif Lindholm <leif.lindholm@linaro.org>
> Cc: Matt Fleming <matt.fleming@intel.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
> Changes since v1:
>  * Added comments to explain the logic of the code.
>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

>  drivers/firmware/dmi_scan.c |   13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> --- linux-4.1-rc1.orig/drivers/firmware/dmi_scan.c      2015-04-30 15:52:43.304650745 +0200
> +++ linux-4.1-rc1/drivers/firmware/dmi_scan.c   2015-04-30 16:16:46.898136915 +0200
> @@ -89,9 +89,9 @@ static void dmi_table(u8 *buf,
>
>         /*
>          * Stop when we have seen all the items the table claimed to have
> -        * (SMBIOS < 3.0 only) OR we reach an end-of-table marker OR we run
> -        * off the end of the table (should never happen but sometimes does
> -        * on bogus implementations.)
> +        * (SMBIOS < 3.0 only) OR we reach an end-of-table marker (SMBIOS
> +        * >= 3.0 only) OR we run off the end of the table (should never
> +        * happen but sometimes does on bogus implementations.)
>          */
>         while ((!dmi_num || i < dmi_num) &&
>                (data - buf + sizeof(struct dmi_header)) <= dmi_len) {
> @@ -110,8 +110,13 @@ static void dmi_table(u8 *buf,
>
>                 /*
>                  * 7.45 End-of-Table (Type 127) [SMBIOS reference spec v3.0.0]
> +                * For tables behind a 64-bit entry point, we have no item
> +                * count and no exact table length, so stop on end-of-table
> +                * marker. For tables behind a 32-bit entry point, we have
> +                * seen OEM structures behind the end-of-table marker on
> +                * some systems, so don't trust it.
>                  */
> -               if (dm->type == DMI_ENTRY_END_OF_TABLE)
> +               if (!dmi_num && dm->type == DMI_ENTRY_END_OF_TABLE)
>                         break;
>
>                 data += 2;
>
>
> --
> Jean Delvare
> SUSE L3 Support