Re: [PATCH 3.2 57/79] ALSA: usb-audio: Fix potential zero-division at parsing FU

Ben Hutchings
2018-02-13T18:29:18Z

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On Mon, 2018-02-12 at 07:59 +0100, Takashi Iwai wrote:
> On Sun, 11 Feb 2018 05:20:06 +0100,
> Ben Hutchings wrote:
> >
> > 3.2.99-rc1 review patch. If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Takashi Iwai <tiwai@suse.de>
> >
> > commit 8428a8ebde2db1e988e41a58497a28beb7ce1705 upstream.
>
> Please drop this. This patch is broken, and was reverted in the later
> commit 3c02a6d94665.

Thanks, I've dropped this from 3.2 and 3.16 patch queues.

Ben.

> thanks,
>
> Takashi
>
>
> >
> > parse_audio_feature_unit() contains a code dividing potentially with
> > zero when a malformed FU descriptor is passed. Although there is
> > already a sanity check, it checks only the value zero, hence it can
> > still lead to a zero-division when a value 1 is passed there.
> >
> > Fix it by correcting the sanity check (and the error message
> > thereof).
> >
> > Fixes: 23caaf19b11e ("ALSA: usb-mixer: Add support for Audio Class v2.0")
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > [bwh: Backported to 3.2: adjust context]
> > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > ---
> > sound/usb/mixer.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > --- a/sound/usb/mixer.c
> > +++ b/sound/usb/mixer.c
> > @@ -1262,9 +1262,9 @@ static int parse_audio_feature_unit(stru
> > return -EINVAL;
> > }
> > csize = hdr->bControlSize;
> > - if (!csize) {
> > + if (csize <= 1) {
> > snd_printdd(KERN_ERR "usbaudio: unit %u: "
> > - "invalid bControlSize == 0\n", unitid);
> > + "invalid bControlSize <= 1\n", unitid);
> > return -EINVAL;
> > }
> > channels = (hdr->bLength - 7) / csize - 1;
> >
--
Ben Hutchings
friends: People who know you well, but like you anyway.

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