Re: [PATCH][next] ALSA: usb-audio: Fix sum of uninitialized variable sample_accum

[Colin Ian King]

On 01/10/2021 11:48, Takashi Iwai wrote:
> On Fri, 01 Oct 2021 12:44:17 +0200,
> Colin King wrote:
> > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >
> > Variable sample_accum is not being intialized and then has
> > ep->sample_rem added to it, leading to a bogus value. One solution
> > is to initialize it to zero at declaration time, but it is probably
> > best to just assign it to ep->sample_rem on first use.
> >
> > Addresses-Coveriry: ("Uninitialized scalar variable")
> > Fixes: f0bd62b64016 ("ALSA: usb-audio: Improve frames size computation")
> > Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> Thanks for the patch, but it's no right fix.  The Fixes tag points to
> a wrong commit, it was d215f63d49da9a8803af3e81acd6cad743686573
>      ALSA: usb-audio: Check available frames for the next packet size
>    
> And sample_accum has to be initialized from ep->sample_accum instead.
> I'll post the proper fix.

Thanks Takshi.

Colin

> Takashi
>
>
> > ---
> >   sound/usb/endpoint.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> > index 42c0d2db8ba8..c6a33732db3f 100644
> > --- a/sound/usb/endpoint.c
> > +++ b/sound/usb/endpoint.c
> > @@ -182,7 +182,7 @@ static int next_packet_size(struct snd_usb_endpoint *ep, unsigned int avail)
> >   	if (ep->fill_max)
> >   		return ep->maxframesize;
> >   
> > -	sample_accum += ep->sample_rem;
> > +	sample_accum = ep->sample_rem;
> >   	if (sample_accum >= ep->pps) {
> >   		sample_accum -= ep->pps;
> >   		ret = ep->packsize[1];
> > --
> > 2.32.0