From b6d93282ccac79e42d87d02652db353894cd1db9 Mon Sep 17 00:00:00 2001 From: Volker Rümelin Date: Fri, 23 Sep 2022 20:36:40 +0200 Subject: audio: prevent an integer overflow in resampling code There are corner cases where rate->opos can overflow. For example, if QEMU is started with -audiodev pa,id=audio0, out.frequency=11025 -device ich9-intel-hda -device hda-duplex, audiodev=audio0 and the guest plays audio with a sampling frequency of 44100Hz, rate->opos will overflow after 27.05h and the audio stream will be silent for a long time. To prevent a rate->opos and also a rate->ipos overflow, both are wrapped around after a short time. The wrap around point rate->ipos >= 0x10001 is an arbitrarily selected value and can be any small value, 0 and 1 included. The comment that an ipos overflow will result in an infinite loop has been removed, because in this case the resampling code only generates no more output samples and the audio stream stalls. However, there is no infinite loop. Signed-off-by: Volker Rümelin Message-Id: <20220923183640.8314-12-vr_qemu@t-online.de> Signed-off-by: Gerd Hoffmann --- audio/rate_template.h | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'audio') diff --git a/audio/rate_template.h b/audio/rate_template.h index f94c940c61..b432719ebb 100644 --- a/audio/rate_template.h +++ b/audio/rate_template.h @@ -72,11 +72,6 @@ void NAME (void *opaque, struct st_sample *ibuf, struct st_sample *obuf, ilast = *ibuf++; rate->ipos++; - /* if ipos overflow, there is a infinite loop */ - if (rate->ipos == 0xffffffff) { - rate->ipos = 1; - rate->opos = rate->opos & 0xffffffff; - } /* See if we finished the input buffer yet */ if (ibuf >= iend) { goto the_end; @@ -85,6 +80,12 @@ void NAME (void *opaque, struct st_sample *ibuf, struct st_sample *obuf, icur = *ibuf; + /* wrap ipos and opos around long before they overflow */ + if (rate->ipos >= 0x10001) { + rate->ipos = 1; + rate->opos &= 0xffffffff; + } + /* interpolate */ #ifdef FLOAT_MIXENG #ifdef RECIPROCAL -- cgit v1.2.3-55-g7522