Re: [PATCH] drm/i915: Fix invalid access to ACPI _DSM objects

[Takashi Iwai <tiwai@suse.de>]

On Fri, 02 Apr 2021 09:47:49 +0200,
Takashi Iwai wrote:
> 
> intel_dsm_platform_mux_info() tries to parse the ACPI package data
> from _DSM for the debug information, but it assumes the fixed format
> without checking what values are stored in the elements actually.
> When an unexpected value is returned from BIOS, it may lead to GPF or
> NULL dereference, as reported recently.
> 
> Add the checks of the contents in the returned values and skip the
> values for invalid cases.
> 
> BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

Scratch this one.  I sent an older version mistakenly.
Will resubmit the right one.


Takashi


> ---
>  drivers/gpu/drm/i915/display/intel_acpi.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> index e21fb14d5e07..492ebc0a8257 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> @@ -84,6 +84,11 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
>  		return;
>  	}
>  
> +	if (!pkg->package.count) {
> +		DRM_DEBUG_DRIVER("no connection in _DSM\n");
> +		return;
> +	}
> +
>  	connector_count = &pkg->package.elements[0];
>  	DRM_DEBUG_DRIVER("MUX info connectors: %lld\n",
>  		  (unsigned long long)connector_count->integer.value);
> @@ -91,6 +96,13 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
>  		union acpi_object *obj = &pkg->package.elements[i];
>  		union acpi_object *connector_id = &obj->package.elements[0];
>  		union acpi_object *info = &obj->package.elements[1];
> +
> +		if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2 ||
> +		    info->type != ACPI_TYPE_BUFFER || info->buffer.length < 4) {
> +			DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
> +			continue;
> +		}
> +
>  		DRM_DEBUG_DRIVER("Connector id: 0x%016llx\n",
>  			  (unsigned long long)connector_id->integer.value);
>  		DRM_DEBUG_DRIVER("  port id: %s\n",
> -- 
> 2.26.2
>