avcodec/alsdec: Fix integer overflow in decode_var_block_data()

Fixes: signed integer overflow: 1927975249 - -514719744 cannot be represented in type 'int'
Fixes: 16413/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5651206856245248
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Thilo Borgmann <thilo.borgmann@mail.de>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index 1fdd0cb0fe07d7817d1de8a2d6235f4a2ed0a16c..11bbd38f582aaf2dae9f37b2d37fe38e9ddaf9f3 100644 (file)
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -951,7 +951,7 @@ static int decode_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
 
         // reconstruct difference signal for prediction (joint-stereo)
         if (bd->js_blocks && bd->raw_other) {
-            int32_t *left, *right;
+            uint32_t *left, *right;
 
             if (bd->raw_other > raw_samples) {  // D = R - L
                 left  = raw_samples;