On 4/15/2021 5:44 PM, Michael Niedermayer wrote:
Fixes: runtime error: signed integer overflow: 65312 * 65535 cannot be 
represented in type 'int'
Fixes: 
32832/clusterfuzz-testcase-minimized-ffmpeg_dem_RM_fuzzer-4817710040088576

Found-by: continuous fuzzing process 
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
---
  libavformat/rmdec.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index fc3bff4859..af032ed90a 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -269,9 +269,9 @@ static int rm_read_audio_stream_info(AVFormatContext *s, 
AVIOContext *pb,
          case DEINT_ID_INT4:
              if (ast->coded_framesize > ast->audio_framesize ||
                  sub_packet_h <= 1 ||
-                ast->coded_framesize * sub_packet_h > (2 + (sub_packet_h & 1)) * 
ast->audio_framesize)
+                ast->coded_framesize * (uint64_t)sub_packet_h > (2 + (sub_packet_h 
& 1)) * ast->audio_framesize)

This check seems superfluous with the one below right after it. ast->coded_framesize * sub_packet_h must be equal to 2 * ast->audio_framesize. It can be removed.

                  return AVERROR_INVALIDDATA;
-            if (ast->coded_framesize * sub_packet_h != 2*ast->audio_framesize) 
{
+            if (ast->coded_framesize * (uint64_t)sub_packet_h != 
2*ast->audio_framesize) {
                  avpriv_request_sample(s, "mismatching interleaver 
parameters");
                  return AVERROR_INVALIDDATA;
              }

How about something like

diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
index fc3bff4859..09880ee3fe 100644
--- a/libavformat/rmdec.c
+++ b/libavformat/rmdec.c
@@ -269,7 +269,7 @@ static int rm_read_audio_stream_info(AVFormatContext *s, 
AVIOContext *pb,
         case DEINT_ID_INT4:
             if (ast->coded_framesize > ast->audio_framesize ||
                 sub_packet_h <= 1 ||
-                ast->coded_framesize * sub_packet_h > (2 + (sub_packet_h & 1)) * 
ast->audio_framesize)
+                ast->audio_framesize > INT_MAX / sub_packet_h)
                 return AVERROR_INVALIDDATA;
             if (ast->coded_framesize * sub_packet_h != 2*ast->audio_framesize) 
{
                 avpriv_request_sample(s, "mismatching interleaver parameters");

Instead?

We already know that ast->coded_framesize is not bigger than ast->audio_framesize, and with this change we'll also know that ast->audio_framesize * sub_packet_h can't overflow, so neither will ast->coded_framesize * sub_packet_h.
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