[FFmpeg-devel] [PATCH v1] avcodec/cbs_vp8: Improve the bitstream position check

[Dai, Jianhui J]

The VP8 compressed header may not be byte-aligned due to boolean
coding. Use bitwise comparison to prevent the potential overread.

Signed-off-by: Jianhui Dai <jianhui.j.dai at intel.com>
---
 libavcodec/cbs_vp8.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavcodec/cbs_vp8.c b/libavcodec/cbs_vp8.c
index 065156c248..13acad3724 100644
--- a/libavcodec/cbs_vp8.c
+++ b/libavcodec/cbs_vp8.c
@@ -327,9 +327,10 @@ static int cbs_vp8_read_unit(CodedBitstreamContext *ctx,
     if (err < 0)
         return err;
 
+    // Position may not be byte-aligned after compressed header; using bits
+    // count comparison for accuracy.
     pos = get_bits_count(&gbc);
-    pos /= 8;
-    av_assert0(pos <= unit->data_size);
+    av_assert0(pos <= unit->data_size * 8);
 
     frame->data_ref = av_buffer_ref(unit->data_ref);
     if (!frame->data_ref)
-- 
2.25.1