Happens when flushing. This triggers NULL + 0 (which is UB) in init_get_bits_xe (which previously errored out, but the return value has not been checked) and in copy_bits(). This fixes the wmavoice-(7|11|19)k FATE-tests with UBSan. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com> --- libavcodec/wmavoice.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/libavcodec/wmavoice.c b/libavcodec/wmavoice.c index 4438089e51..26744719e6 100644 --- a/libavcodec/wmavoice.c +++ b/libavcodec/wmavoice.c @@ -1900,6 +1900,8 @@ static int wmavoice_decode_packet(AVCodecContext *ctx, AVFrame *frame, { WMAVoiceContext *s = ctx->priv_data; GetBitContext *gb = &s->gb; + const uint8_t *buf = avpkt->data; + uint8_t dummy[1]; int size, res, pos; /* Packets are sometimes a multiple of ctx->block_align, with a packet @@ -1908,7 +1910,8 @@ static int wmavoice_decode_packet(AVCodecContext *ctx, AVFrame *frame, * in a single "muxer" packet, so we artificially emulate that by * capping the packet size at ctx->block_align. */ for (size = avpkt->size; size > ctx->block_align; size -= ctx->block_align); - init_get_bits8(&s->gb, avpkt->data, size); + buf = size ? buf : dummy; + init_get_bits8(&s->gb, buf, size); /* size == ctx->block_align is used to indicate whether we are dealing with * a new packet or a packet of which we already read the packet header @@ -1931,7 +1934,7 @@ static int wmavoice_decode_packet(AVCodecContext *ctx, AVFrame *frame, if (cnt + s->spillover_nbits > avpkt->size * 8) { s->spillover_nbits = avpkt->size * 8 - cnt; } - copy_bits(&s->pb, avpkt->data, size, gb, s->spillover_nbits); + copy_bits(&s->pb, buf, size, gb, s->spillover_nbits); flush_put_bits(&s->pb); s->sframe_cache_size += s->spillover_nbits; if ((res = synth_superframe(ctx, frame, got_frame_ptr)) == 0 && @@ -1968,7 +1971,7 @@ static int wmavoice_decode_packet(AVCodecContext *ctx, AVFrame *frame, } else if ((s->sframe_cache_size = pos) > 0) { /* ... cache it for spillover in next packet */ init_put_bits(&s->pb, s->sframe_cache, SFRAME_CACHE_MAXSIZE); - copy_bits(&s->pb, avpkt->data, size, gb, s->sframe_cache_size); + copy_bits(&s->pb, buf, size, gb, s->sframe_cache_size); // FIXME bad - just copy bytes as whole and add use the // skip_bits_next field } -- 2.34.1