[FFmpeg-cvslog] avcodec/cbs_h2645: Avoid an unchecked bytesteram read

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Jul 25 02:13:10 2023 +0200| [0ba719f726632d73592311615087a0d64aa2fb60] | committer: Michael Niedermayer

avcodec/cbs_h2645: Avoid an unchecked bytesteram read

The unchecked read caused the 2nd subsequent tell call to move backward resulting
in a negative length

Fixes: assertion failure
Fixes: 60276/clusterfuzz-testcase-minimized-ffmpeg_BSF_TRACE_HEADERS_fuzzer-5434126636023808

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: James Almer <jamrial at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0ba719f726632d73592311615087a0d64aa2fb60
---

 libavcodec/cbs_h2645.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
index 34c5d1d372..21c8bc76d5 100644
--- a/libavcodec/cbs_h2645.c
+++ b/libavcodec/cbs_h2645.c
@@ -695,7 +695,7 @@ static int cbs_h2645_split_fragment(CodedBitstreamContext *ctx,
             int nal_unit_type = bytestream2_get_byte(&gbc) & 0x1f;
             unsigned int num_nalus = 1;
             if(nal_unit_type != VVC_DCI_NUT && nal_unit_type != VVC_OPI_NUT)
-                num_nalus = bytestream2_get_be16u(&gbc);
+                num_nalus = bytestream2_get_be16(&gbc);
 
             start = bytestream2_tell(&gbc);
             for(i = 0; i < num_nalus; i++) {