[Intel-gfx] [PATCH] drm/i915/bios: handle MIPI Sequence Block v3+ gracefully

[Deepak, M]

Reviewed-by: Deepak M <m.deepak at intel.com>

>-----Original Message-----
>From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel
>Vetter
>Sent: Wednesday, September 23, 2015 7:02 PM
>To: Nikula, Jani
>Cc: intel-gfx at lists.freedesktop.org; Deepak, M
>Subject: Re: [Intel-gfx] [PATCH] drm/i915/bios: handle MIPI Sequence Block
>v3+ gracefully
>
>On Thu, Sep 17, 2015 at 04:42:07PM +0300, Jani Nikula wrote:
>> The VBT MIPI Sequence Block version 3 has forward incompatible changes:
>>
>> First, the block size in the header has been specified reserved, and
>> the actual size is a separate 32-bit value within the block. The
>> current
>> find_section() function to will only look at the size in the block
>> header, and, depending on what's in that now reserved size field,
>> continue looking for other sections in the wrong place.
>>
>> Fix this by taking the new block size field into account. This will
>> ensure that the lookups for other sections will work properly, as long
>> as the new 32-bit size does not go beyond the opregion VBT mailbox size.
>>
>> Second, the contents of the block have been completely changed.
>> Gracefully refuse parsing the yet unknown data version.
>>
>> Cc: Deepak M <m.deepak at intel.com>
>> Cc: stable at vger.kernel.org
>> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>
>Deepak, ping for review.
>-Daniel
>
>> ---
>>  drivers/gpu/drm/i915/intel_bios.c | 12 +++++++++++-
>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_bios.c
>> b/drivers/gpu/drm/i915/intel_bios.c
>> index c8acc2952f82..68421c273c8c 100644
>> --- a/drivers/gpu/drm/i915/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/intel_bios.c
>> @@ -42,7 +42,7 @@ find_section(const void *_bdb, int section_id)
>>  	const struct bdb_header *bdb = _bdb;
>>  	const u8 *base = _bdb;
>>  	int index = 0;
>> -	u16 total, current_size;
>> +	u32 total, current_size;
>>  	u8 current_id;
>>
>>  	/* skip to first section */
>> @@ -57,6 +57,10 @@ find_section(const void *_bdb, int section_id)
>>  		current_size = *((const u16 *)(base + index));
>>  		index += 2;
>>
>> +		/* The MIPI Sequence Block v3+ has a separate size field. */
>> +		if (current_id == BDB_MIPI_SEQUENCE && *(base + index) >=
>3)
>> +			current_size = *((const u32 *)(base + index + 1));
>> +
>>  		if (index + current_size > total)
>>  			return NULL;
>>
>> @@ -799,6 +803,12 @@ parse_mipi(struct drm_i915_private *dev_priv,
>const struct bdb_header *bdb)
>>  		return;
>>  	}
>>
>> +	/* Fail gracefully for forward incompatible sequence block. */
>> +	if (sequence->version >= 3) {
>> +		DRM_ERROR("Unable to parse MIPI Sequence Block v3+\n");
>> +		return;
>> +	}
>> +
>>  	DRM_DEBUG_DRIVER("Found MIPI sequence block\n");
>>
>>  	block_size = get_blocksize(sequence);
>> --
>> 2.1.4
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>--
>Daniel Vetter
>Software Engineer, Intel Corporation
>http://blog.ffwll.ch