Re: [Xen-devel] [PATCH] ALSA: xen-front: fix unintention integer overflow on left shifts

[Oleksandr Andrushchenko]

On 6/28/19 11:46 AM, Takashi Iwai wrote:
> On Thu, 27 Jun 2019 18:58:53 +0200,
> Colin King wrote:
> > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >
> > Shifting the integer value 1 is evaluated using 32-bit
> > arithmetic and then used in an expression that expects a 64-bit
> > value, so there is potentially an integer overflow. Fix this
> > by using the BIT_ULL macro to perform the shift.
> >
> > Addresses-Coverity: ("Unintentional integer overflow")
> > Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Thank you for you patch,
Oleksandr
> The fix is correct, but luckily we didn't hit the integer overflow, as
> all passed values are less than 32bit.
>
> In anyway, applied now.  Thanks.
>
>
> Takashi
>
> > ---
> >   sound/xen/xen_snd_front_alsa.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/sound/xen/xen_snd_front_alsa.c b/sound/xen/xen_snd_front_alsa.c
> > index b14ab512c2ce..e01631959ed8 100644
> > --- a/sound/xen/xen_snd_front_alsa.c
> > +++ b/sound/xen/xen_snd_front_alsa.c
> > @@ -196,7 +196,7 @@ static u64 to_sndif_formats_mask(u64 alsa_formats)
> >   	mask = 0;
> >   	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
> >   		if (pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa) & alsa_formats)
> > -			mask |= 1 << ALSA_SNDIF_FORMATS[i].sndif;
> > +			mask |= BIT_ULL(ALSA_SNDIF_FORMATS[i].sndif);
> >   
> >   	return mask;
> >   }
> > @@ -208,7 +208,7 @@ static u64 to_alsa_formats_mask(u64 sndif_formats)
> >   
> >   	mask = 0;
> >   	for (i = 0; i < ARRAY_SIZE(ALSA_SNDIF_FORMATS); i++)
> > -		if (1 << ALSA_SNDIF_FORMATS[i].sndif & sndif_formats)
> > +		if (BIT_ULL(ALSA_SNDIF_FORMATS[i].sndif) & sndif_formats)
> >   			mask |= pcm_format_to_bits(ALSA_SNDIF_FORMATS[i].alsa);
> >   
> >   	return mask;
> > --
> > 2.20.1
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