if(b->sample_count>v->granulepos){
/* corner case; if this is both the first and last audio page,
then spec says the end is cut, not beginning */
+ long extra=b->sample_count-vb->granulepos;
+
+ /* we use ogg_int64_t for granule positions because a
+ uint64 isn't universally available. Unfortunately,
+ that means granposes can be 'negative' and result in
+ extra being negative */
+ if(extra<0)
+ extra=0;
+
if(vb->eofflag){
/* trim the end */
/* no preceding granulepos; assume we started at zero (we'd
/* granulepos could be -1 due to a seek, but that would result
in a long count, not short count */
- v->pcm_current-=(b->sample_count-v->granulepos)>>hs;
+ /* Guard against corrupt/malicious frames that set EOP and
+ a backdated granpos; don't rewind more samples than we
+ actually have */
+ if(extra > (v->pcm_current - v->pcm_returned)<<hs)
+ extra = (v->pcm_current - v->pcm_returned)<<hs;
+
+ v->pcm_current-=extra>>hs;
}else{
/* trim the beginning */
- v->pcm_returned+=(b->sample_count-v->granulepos)>>hs;
+ v->pcm_returned+=extra>>hs;
if(v->pcm_returned>v->pcm_current)
v->pcm_returned=v->pcm_current;
}
if(extra)
if(vb->eofflag){
/* partial last frame. Strip the extra samples off */
+
+ /* Guard against corrupt/malicious frames that set EOP and
+ a backdated granpos; don't rewind more samples than we
+ actually have */
+ if(extra > (v->pcm_current - v->pcm_returned)<<hs)
+ extra = (v->pcm_current - v->pcm_returned)<<hs;
+
+ /* we use ogg_int64_t for granule positions because a
+ uint64 isn't universally available. Unfortunately,
+ that means granposes can be 'negative' and result in
+ extra being negative */
+ if(extra<0)
+ extra=0;
+
v->pcm_current-=extra>>hs;
} /* else {Shouldn't happen *unless* the bitstream is out of
spec. Either way, believe the bitstream } */