[FFmpeg-devel] [PATCH] avcodec/alsdec: Consider frame_size in ra_block handling

[Michael Niedermayer]

Fixes: out of array access
Fixes: 15277/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5184853437317120

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/alsdec.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index e50a287f19..f94086efcb 100644
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -789,14 +789,15 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
 
     // read first value and residuals in case of a random access block
     if (bd->ra_block) {
-        if (opt_order)
+        int len = FFMIN(opt_order, sconf->frame_length);
+        if (len)
             bd->raw_samples[0] = decode_rice(gb, avctx->bits_per_raw_sample - 4);
-        if (opt_order > 1)
+        if (len > 1)
             bd->raw_samples[1] = decode_rice(gb, FFMIN(s[0] + 3, ctx->s_max));
-        if (opt_order > 2)
+        if (len > 2)
             bd->raw_samples[2] = decode_rice(gb, FFMIN(s[0] + 1, ctx->s_max));
 
-        start = FFMIN(opt_order, 3);
+        start = FFMIN(len, 3);
     }
 
     // read all residuals
-- 
2.22.0