On 6/5/2025 9:29 PM, Andreas Rheinhardt wrote:
James Almer:
The GetBitContext API requires the buffer to be padded, and the documentation 
for
av_ac3_parse_header() does not specify it, so use a temporary local buffer.

Signed-off-by: James Almer <jamr...@gmail.com>
---
  libavcodec/ac3_parser.c | 16 +++++++++++++---
  1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/libavcodec/ac3_parser.c b/libavcodec/ac3_parser.c
index 69989690dd..9065d700e2 100644
--- a/libavcodec/ac3_parser.c
+++ b/libavcodec/ac3_parser.c
@@ -202,14 +202,24 @@ int av_ac3_parse_header(const uint8_t *buf, size_t size,
  {
      GetBitContext gb;
      AC3HeaderInfo hdr;
+    uint8_t *tmp = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
      int err;
- err = init_get_bits8(&gb, buf, size);
-    if (err < 0)
+    if (!tmp)
+        return AVERROR(ENOMEM);
+
+    memcpy(tmp, buf, size);
+    memset(tmp + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+    err = init_get_bits8(&gb, tmp, size);
+    if (err < 0) {
+        av_free(tmp);
          return AVERROR_INVALIDDATA;
+    }
      err = ff_ac3_parse_header(&gb, &hdr);
-    if (err < 0)
+    if (err < 0) {
+        av_free(tmp);
          return AVERROR_INVALIDDATA;
+    }
*bitstream_id = hdr.bitstream_id;
      *frame_size   = hdr.frame_size;

There is no need for an allocation here; (E)AC-3 frames have a bounded
size and the number of bytes read by ff_ac3_parse_header() is even smaller.

What's the max size? Is there a define for it?

Anyway: The buffer leaks on success.

I'm aware, i said as much in a reply :p


- Andreas

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