[FFmpeg-devel] [PATCH] lavc/vvc: Error on inter slice with no reference pics (PR #21293)

[frankplow via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21293 opened by frankplow
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21293
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21293.patch

The semantics of sh_num_ref_idx_active_minus1[ i ] state that

When the current slice is a P slice, the value of NumRefIdxActive[ 0 ] shall be greater than 0.
When the current slice is a B slice, both NumRefIdxActive[ 0 ] and NumRefIdxActive[ 1 ] shall be greater than 0.

Fixes: use of uninitialized memory
Fixes: 449549597/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VVC_fuzzer-5600497089445888

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reported-by: Michael Niedermayer michael@niedermayer.cc


>From 1a8e41b710cfefb5eabfb6d1e31a1e8258078342 Mon Sep 17 00:00:00 2001
From: Frank Plowman <post@frankplowman.com>
Date: Wed, 24 Dec 2025 15:35:06 +0000
Subject: [PATCH] lavc/vvc: Error on inter slice with no reference pics

The semantics of sh_num_ref_idx_active_minus1[ i ] state that

When the current slice is a P slice, the value of NumRefIdxActive[ 0 ] shall be greater than 0.
When the current slice is a B slice, both NumRefIdxActive[ 0 ] and NumRefIdxActive[ 1 ] shall be greater than 0.

Fixes: use of uninitialized memory
Fixes: 449549597/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VVC_fuzzer-5600497089445888

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reported-by: Michael Niedermayer michael@niedermayer.cc
---
 libavcodec/cbs_h266_syntax_template.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libavcodec/cbs_h266_syntax_template.c b/libavcodec/cbs_h266_syntax_template.c
index 8b337c75d0..d9a65a9c19 100644
--- a/libavcodec/cbs_h266_syntax_template.c
+++ b/libavcodec/cbs_h266_syntax_template.c
@@ -3248,6 +3248,12 @@ static int FUNC(slice_header) (CodedBitstreamContext *ctx, RWContext *rw,
                     FFMIN(ref_pic_lists->rpl_ref_list[i].num_ref_entries,
                         pps->pps_num_ref_idx_default_active_minus1[i] + 1);
             }
+
+            if (current->num_ref_idx_active[i] <= 0) {
+                av_log(ctx->log_ctx, AV_LOG_ERROR,
+                       "Inter slice but no reference pictures available for RPL%d.\n", i);
+                return AVERROR_INVALIDDATA;
+            }
         } else {
             current->num_ref_idx_active[i] = 0;
         }
-- 
2.49.1

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