[FFmpeg-devel] [PATCH] avformat/iamf_parse: increase PutBytes buffer when writing AAC extradata

[James Almer]

We may write up to 43 bits, so 5 bytes is not enough.

Fixes: Assertion n>=0 && n<=32 failed at ./libavcodec/get_bits.h:406
Fixes: 398527871/clusterfuzz-testcase-minimized-ffmpeg_dem_IAMF_fuzzer-6602025714647040

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavformat/iamf_parse.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavformat/iamf_parse.c b/libavformat/iamf_parse.c
index abedfdb066..11c27ebe98 100644
--- a/libavformat/iamf_parse.c
+++ b/libavformat/iamf_parse.c
@@ -285,7 +285,7 @@ static int update_extradata(AVCodecParameters *codecpar)
         AV_WL16A(codecpar->extradata + 16, AV_RB16A(codecpar->extradata + 16)); // Byte swap Output Gain
         break;
     case AV_CODEC_ID_AAC: {
-        uint8_t buf[5];
+        uint8_t buf[6];
 
         init_put_bits(&pb, buf, sizeof(buf));
         ret = init_get_bits8(&gb, codecpar->extradata, codecpar->extradata_size);
@@ -304,6 +304,10 @@ static int update_extradata(AVCodecParameters *codecpar)
         skip_bits(&gb, 4);
         put_bits(&pb, 4, codecpar->ch_layout.nb_channels); // set channel config
         ret = put_bits_left(&pb);
+        while (ret >= 32) {
+           put_bits32(&pb, get_bits_long(&gb, 32));
+           ret -= 32;
+        }
         put_bits(&pb, ret, get_bits_long(&gb, ret));
         flush_put_bits(&pb);
 
-- 
2.49.0