avcodec/adpcm: Fix invalid shifts in ADPCM DTK

Fixes: left shift of negative value -1
Fixes: 18397/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ADPCM_DTK_fuzzer-5675653487132672
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c
index a8e74522b3b4125450fe2120f38dd366d9fdc233..53d8d0be6a164af21c92adc2f47b97621181585e 100644 (file)
--- a/libavcodec/adpcm.c
+++ b/libavcodec/adpcm.c
@@ -1723,7 +1723,7 @@ static int adpcm_decode_frame(AVCodecContext *avctx, void *data,
                     else
                         sampledat = sign_extend(byte >> 4, 4);
 
-                    sampledat = (((sampledat << 12) >> (header & 0xf)) << 6) + prev;
+                    sampledat = ((sampledat * (1 << 12)) >> (header & 0xf)) * (1 << 6) + prev;
                     *samples++ = av_clip_int16(sampledat >> 6);
                     c->status[channel].sample2 = c->status[channel].sample1;
                     c->status[channel].sample1 = sampledat;