On Mon, Mar 29, 2021 at 04:37:21PM +0300, Jani Nikula wrote:
The DisplayID specifications explicitly call out 0 as a valid payload length for data blocks. The mere presence of a data block, or the information coded in the block specific data (bits 7:3 in offset 1), may be enough to convey the necessary information.
Signed-off-by: Jani Nikula jani.nikula@intel.com
Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com
Though after looking at the current users it looks to me like we're missing some block length checks. In particular drm_parse_tiled_block() looks suspect. Judging by what I wrote in cea_db_offsets() I think I once convinced myself that the CEA ext block stuff is safe. And add_displayid_detailed_1_modes() looks OK as well.
drivers/gpu/drm/drm_displayid.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_displayid.c b/drivers/gpu/drm/drm_displayid.c index 902ff6114b68..e0b9e58a9dc8 100644 --- a/drivers/gpu/drm/drm_displayid.c +++ b/drivers/gpu/drm/drm_displayid.c @@ -77,8 +77,7 @@ displayid_iter_block(const struct displayid_iter *iter) block = (const struct displayid_block *)&iter->section[iter->idx];
if (iter->idx + sizeof(*block) <= iter->length &&
iter->idx + sizeof(*block) + block->num_bytes <= iter->length &&block->num_bytes > 0)
iter->idx + sizeof(*block) + block->num_bytes <= iter->length)return block;
return NULL;
-- 2.20.1