[FFmpeg-devel] [PATCH v2 2/2] lavc/vvc: Prevent overflow in chroma QP derivation

[Frank Plowman]

On the top of p. 112 in VVC (09/2023):

It is a requirement of bitstream conformance that the values of
qpInVal[ i ][ j ] and qpOutVal[ i ][ j ] shall be in the range
of −QpBdOffset to 63, inclusive for i in the range of 0 to
numQpTables − 1, inclusive, and j in the range of 0 to
sps_num_points_in_qp_table_minus1[ i ] + 1, inclusive.

Signed-off-by: Frank Plowman <post at frankplowman.com>
---
 libavcodec/vvc/ps.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavcodec/vvc/ps.c b/libavcodec/vvc/ps.c
index bfc3c121fd..c4f64d5da7 100644
--- a/libavcodec/vvc/ps.c
+++ b/libavcodec/vvc/ps.c
@@ -101,9 +101,14 @@ static int sps_chroma_qp_table(VVCSPS *sps)
 
         qp_out[0] = qp_in[0] = r->sps_qp_table_start_minus26[i] + 26;
         for (int j = 0; j < num_points_in_qp_table; j++ ) {
+            const uint8_t delta_qp_out = (r->sps_delta_qp_in_val_minus1[i][j] ^ r->sps_delta_qp_diff_val[i][j]);
             delta_qp_in[j] = r->sps_delta_qp_in_val_minus1[i][j] + 1;
+            if (qp_in[j] + delta_qp_in[j] > 63)
+                return AVERROR(EINVAL);
             qp_in[j+1] = qp_in[j] + delta_qp_in[j];
-            qp_out[j+1] = qp_out[j] + (r->sps_delta_qp_in_val_minus1[i][j] ^ r->sps_delta_qp_diff_val[i][j]);
+            if (qp_out[j] + delta_qp_out > 63)
+                return AVERROR(EINVAL);
+            qp_out[j+1] = qp_out[j] + delta_qp_out;
         }
         sps->chroma_qp_table[i][qp_in[0] + off] = qp_out[0];
         for (int k = qp_in[0] - 1 + off; k >= 0; k--)
-- 
2.45.1