media: vicodec: Handle the case that the reference buffer is NULL

In the stateless decoder the reference buffer is null if the
frame is an I-frame (flagged with FWHT_FL_I_FRAME).
Make sure not to dereference it in that case.
Signed-off-by: Dafna Hirschfeld <dafna3@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/vicodec/codec-fwht.c

@@ -841,6 +841,7 @@ static bool decode_plane(struct fwht_cframe *cf, const __be16 **rlco,
 	s16 copy[8 * 8];
 	u16 stat;
 	unsigned int i, j;
+	bool is_intra = !ref;
 
 	width = round_up(width, 8);
 	height = round_up(height, 8);
@@ -872,7 +873,7 @@ static bool decode_plane(struct fwht_cframe *cf, const __be16 **rlco,
 
 			if (copies) {
 				memcpy(cf->de_fwht, copy, sizeof(copy));
-				if (stat & PFRAME_BIT)
+				if ((stat & PFRAME_BIT) && !is_intra)
 					add_deltas(cf->de_fwht, refp,
 						   ref_stride, ref_step);
 				fill_decoder_block(dstp, cf->de_fwht,
@@ -884,18 +885,18 @@ static bool decode_plane(struct fwht_cframe *cf, const __be16 **rlco,
 			stat = derlc(rlco, cf->coeffs, end_of_rlco_buf);
 			if (stat & OVERFLOW_BIT)
 				return false;
-			if (stat & PFRAME_BIT)
+			if ((stat & PFRAME_BIT) && !is_intra)
 				dequantize_inter(cf->coeffs);
 			else
 				dequantize_intra(cf->coeffs);
 
 			ifwht(cf->coeffs, cf->de_fwht,
-			      (stat & PFRAME_BIT) ? 0 : 1);
+			      ((stat & PFRAME_BIT) && !is_intra) ? 0 : 1);
 
 			copies = (stat & DUPS_MASK) >> 1;
 			if (copies)
 				memcpy(copy, cf->de_fwht, sizeof(copy));
-			if (stat & PFRAME_BIT)
+			if ((stat & PFRAME_BIT) && !is_intra)
 				add_deltas(cf->de_fwht, refp,
 					   ref_stride, ref_step);
 			fill_decoder_block(dstp, cf->de_fwht, dst_stride,

drivers/media/platform/vicodec/codec-v4l2-fwht.c

@@ -99,6 +99,17 @@ static int prepare_raw_frame(struct fwht_raw_frame *rf,
 	rf->alpha = NULL;
 	rf->components_num = info->components_num;
 
+	/*
+	 * The buffer is NULL if it is the reference
+	 * frame of an I-frame in the stateless decoder
+	 */
+	if (!buf) {
+		rf->luma = NULL;
+		rf->cb = NULL;
+		rf->cr = NULL;
+		rf->alpha = NULL;
+		return 0;
+	}
 	switch (info->id) {
 	case V4L2_PIX_FMT_GREY:
 		rf->cb = NULL;