ACPI: SPCR: Check for table version when using precise baudrate

[PATCH] ACPI: SPCR: Check for table version when using precise baudrate

Posted by Punit Agrawal 3 months, 2 weeks ago

Commit 4d330fe54145 ("ACPI: SPCR: Support Precise Baud Rate field")
added support to use the precise baud rate available since SPCR
1.09 (revision 4) but failed to check the version of the table
provided by the firmware. Accessing an older version of SPCR table
causes accesses beyond the end of the table and can lead to garbage
data to be used for the baud rate.

Check the version of the firmware provided SPCR to ensure that the
precise baudrate is vaild before using it.

Fixes: 4d330fe54145 ("ACPI: SPCR: Support Precise Baud Rate field")
Signed-off-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com>
---
 drivers/acpi/spcr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index d4d52d5e9016..73cb933fdc89 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -155,7 +155,7 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
 	 * Baud Rate field. If this field is zero or not present, Configured
 	 * Baud Rate is used.
 	 */
-	if (table->precise_baudrate)
+	if (table->header.revision >= 4 && table->precise_baudrate)
 		baud_rate = table->precise_baudrate;
 	else switch (table->baud_rate) {
 	case 0:
-- 
2.34.1

Re: [PATCH] ACPI: SPCR: Check for table version when using precise baudrate

Posted by Rafael J. Wysocki 3 months, 1 week ago

On Fri, Oct 24, 2025 at 2:31 PM Punit Agrawal
<punit.agrawal@oss.qualcomm.com> wrote:
>
> Commit 4d330fe54145 ("ACPI: SPCR: Support Precise Baud Rate field")
> added support to use the precise baud rate available since SPCR
> 1.09 (revision 4) but failed to check the version of the table
> provided by the firmware. Accessing an older version of SPCR table
> causes accesses beyond the end of the table and can lead to garbage
> data to be used for the baud rate.
>
> Check the version of the firmware provided SPCR to ensure that the
> precise baudrate is vaild before using it.
>
> Fixes: 4d330fe54145 ("ACPI: SPCR: Support Precise Baud Rate field")
> Signed-off-by: Punit Agrawal <punit.agrawal@oss.qualcomm.com>
> ---
>  drivers/acpi/spcr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
> index d4d52d5e9016..73cb933fdc89 100644
> --- a/drivers/acpi/spcr.c
> +++ b/drivers/acpi/spcr.c
> @@ -155,7 +155,7 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
>          * Baud Rate field. If this field is zero or not present, Configured
>          * Baud Rate is used.
>          */
> -       if (table->precise_baudrate)
> +       if (table->header.revision >= 4 && table->precise_baudrate)
>                 baud_rate = table->precise_baudrate;
>         else switch (table->baud_rate) {
>         case 0:
> --

Applied as 6.18-rc material, thanks!