[FFmpeg-devel] [PATCH 3/3] avcodec/apedec: Make coeffsA/B uint32_t, this avoids several cases of undefined behavior

[Michael Niedermayer]

Changing the type to an unsigned one to avoid many casts was suggested
This may be inadequate for fixing the UB on ILP64

Fixes: signed integer overflow: -1418162611 * 383 cannot be represented in type 'int'
Fixes: 15547/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_APE_fuzzer-5691384901664768

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/apedec.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libavcodec/apedec.c b/libavcodec/apedec.c
index 7a7097e7a4..e9ffdfdcdf 100644
--- a/libavcodec/apedec.c
+++ b/libavcodec/apedec.c
@@ -125,8 +125,8 @@ typedef struct APEPredictor {
     int32_t filterA[2];
     int32_t filterB[2];
 
-    int32_t coeffsA[2][4];  ///< adaption coefficients
-    int32_t coeffsB[2][5];  ///< adaption coefficients
+    uint32_t coeffsA[2][4];  ///< adaption coefficients
+    uint32_t coeffsB[2][5];  ///< adaption coefficients
     int32_t historybuffer[HISTORY_SIZE + PREDICTOR_SIZE];
 
     unsigned int sample_pos;
@@ -829,7 +829,7 @@ static av_always_inline int filter_fast_3320(APEPredictor *p,
     }
 
     predictionA = p->buf[delayA] * 2 - p->buf[delayA - 1];
-    p->lastA[filter] = decoded + (predictionA  * p->coeffsA[filter][0] >> 9);
+    p->lastA[filter] = decoded + ((int32_t)(predictionA  * p->coeffsA[filter][0]) >> 9);
 
     if ((decoded ^ predictionA) > 0)
         p->coeffsA[filter][0]++;
-- 
2.22.0