[PATCH] ALSA: hda: ignore invalid NHLT table

[Pierre-Louis Bossart]

Adding Mark, Takashi, Jaroslav and Cezary in Cc:

On 3/2/21 8:10 AM, Mark Pearson wrote:
> On some Lenovo systems if the microphone is disabled in the BIOS
> only the NHLT table header is created, with no data. This means
> the endpoints field is not correctly set to zero - leading to an
> unintialised variable and hence invalid descriptors are parsed
> leading to page faults.
> 
> The Lenovo firmware team is addressing this, but adding a check
> preventing invalid tables being parsed is worthwhile.
> 
> Tested on a Lenovo T14.
> 
> Tested-by: Philipp Leskovitz <philipp.leskovitz at secunet.com>
> Reported-by: Philipp Leskovitz <philipp.leskovitz at secunet.com>
> Signed-off-by: Mark Pearson <markpearson at lenovo.com>

The change looks good to me

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>

Out of curiosity, does this impact Kabylake or CometLake+ systems?

Thanks!

> ---
>   sound/hda/intel-nhlt.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/sound/hda/intel-nhlt.c b/sound/hda/intel-nhlt.c
> index 059aaf04f..0889f2cc5 100644
> --- a/sound/hda/intel-nhlt.c
> +++ b/sound/hda/intel-nhlt.c
> @@ -37,6 +37,11 @@ int intel_nhlt_get_dmic_geo(struct device *dev, struct nhlt_acpi_table *nhlt)
>   	if (!nhlt)
>   		return 0;
>   
> +	if (nhlt->header.length <= sizeof(struct acpi_table_header)) {
> +		dev_warn(dev, "Invalid DMIC description table\n");
> +		return 0;
> +	}
> +
>   	epnt = (struct nhlt_endpoint *)nhlt->desc;
>   
>   	for (j = 0; j < nhlt->endpoint_count; j++) {
>