media: v4l2-ctrls: validate HEVC active reference counts

media: v4l2-ctrls: validate HEVC active reference counts

HEVC slice parameters are shared stateless V4L2 controls, but the common
validation path does not verify the active L0/L1 reference counts before
driver-specific code consumes them.

The original report came from Cedrus, but the active count bounds are
not Cedrus-specific. Validate them in the common HEVC slice control path
so stateless HEVC drivers get the same basic guarantees as soon as the
control is queued.

Do not reject ref_idx_l0/ref_idx_l1 entries here. Existing userspace may
use out-of-range sentinel values such as 0xff for missing references, and
some hardware can use that information for concealment. Keep this common
check limited to the active reference counts.

Fixes: d395a78db9eab ("media: hevc: Add decode params control")
Cc: stable@vger.kernel.org
Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>