media: cedrus: skip invalid H.264 reference list entries

media: cedrus: skip invalid H.264 reference list entries

Cedrus consumes H.264 ref_pic_list0/ref_pic_list1 entries from the
stateless slice control and later uses their indices to look up
decode->dpb[] in _cedrus_write_ref_list().

Rejecting such controls in cedrus_try_ctrl() would break existing
userspace, since stateless H.264 reference lists may legitimately carry
out-of-range indices for missing references. Instead, guard the actual
DPB lookup in Cedrus and skip entries whose indices do not fit the fixed
V4L2_H264_NUM_DPB_ENTRIES array.

This keeps the fix local to the driver use site and avoids out-of-bounds
reads from malformed or unsupported reference list entries.

Fixes: e000e1fa4bdbd ("media: uapi: h264: Update reference lists")
Cc: stable@vger.kernel.org
Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Tested-by: Chen-Yu Tsai <wens@kernel.org>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>