On Fri, Apr 02, 2021 at 10:23:17AM +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.
>
> v1->v2: Check the info contents before dereferencing, too
>
> BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
> Cc: <sta...@vger.kernel.org>
> Signed-off-by: Takashi Iwai <ti...@suse.de>
> ---
> drivers/gpu/drm/i915/display/intel_acpi.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c
> b/drivers/gpu/drm/i915/display/intel_acpi.c
> index e21fb14d5e07..833d0c1be4f1 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> @@ -84,13 +84,31 @@ 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);
> for (i = 1; i < pkg->package.count; i++) {
> 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];
> + union acpi_object *connector_id;
> + union acpi_object *info;
> +
> + if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2) {
> + DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
> + continue;
> + }
> +
> + connector_id = &obj->package.elements[0];
You don't want to check connector_id->type as well?
> + info = &obj->package.elements[1];
> + if (info->type != ACPI_TYPE_BUFFER || info->buffer.length < 4) {
> + DRM_DEBUG_DRIVER("Invalid info for MUX obj #%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
>
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> intel-...@lists.freedesktop.org
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--
Ville Syrjälä
Intel
