On 7/11/2019 6:49 PM, Michael Niedermayer wrote:
> Fixes: left shift of negative value -456
> Fixes:
> 15561/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPC8_fuzzer-5758130404720640
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <[email protected]>
> ---
> libavcodec/mpc8.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/mpc8.c b/libavcodec/mpc8.c
> index 3be2f79a5a..75943064da 100644
> --- a/libavcodec/mpc8.c
> +++ b/libavcodec/mpc8.c
> @@ -364,7 +364,7 @@ static int mpc8_decode_frame(AVCodecContext * avctx, void
> *data,
> for(j = 0; j < SAMPLES_PER_BAND; j += SAMPLES_PER_BAND / 2){
> cnt = get_vlc2(gb, q1_vlc.table, MPC8_Q1_BITS, 2);
> t = mpc8_get_mask(gb, 18, cnt);
> - for(k = 0; k < SAMPLES_PER_BAND / 2; k++, t <<= 1)
> + for(k = 0; k < SAMPLES_PER_BAND / 2; k++, t +=
> (unsigned)t)
How about something like this instead (Untested)
for(k = 0; k < SAMPLES_PER_BAND / 2; k++)
c->Q[ch][off + j + k] = t & (1 << (SAMPLES_PER_BAND / 2 - k - 1))
? (get_bits1(gb) << 1) - 1 : 0;
> c->Q[ch][off + j + k] = (t & 0x20000) ?
> (get_bits1(gb) << 1) - 1 : 0;
> }
> break;
>
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