linux-kernel - Re: [PATCH] media: flexcop-usb: fix sanity check of bNumEndpoints

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Date:   Thu, 9 Jun 2022 09:42:15 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Dongliang Mu <dzm91@...t.edu.cn>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        gushengxian <gushengxian@...ong.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Oliver Neukum <oneukum@...e.com>, Sean Young <sean@...s.org>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        linux-media@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: flexcop-usb: fix sanity check of bNumEndpoints

On Thu, Jun 2, 2022 at 2:45 PM Johan Hovold <johan@...nel.org> wrote:
>
> On Thu, Jun 02, 2022 at 01:50:24PM +0800, Dongliang Mu wrote:
> > From: Dongliang Mu <mudongliangabcd@...il.com>
> >
> > Commit d725d20e81c2 ("media: flexcop-usb: sanity checking of endpoint type
> > ") adds a sanity check for endpoint[1], but fails to modify the sanity
> > check of bNumEndpoints.
> >
> > Fix this by modifying the sanity check of bNumEndpoints to 2.
>
> Are you sure that d725d20e81c2 ("media: flexcop-usb: sanity checking of
> endpoint type) was correct?

I am not sure if fc_usb->uintf->cur_altsetting->endpoint[1] is right or not.

But the sanity check of bNumEndpoints does not match the following dereference.

>
> > Fixes: d725d20e81c2 ("media: flexcop-usb: sanity checking of endpoint type")
> > Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> > ---
> >  drivers/media/usb/b2c2/flexcop-usb.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/usb/b2c2/flexcop-usb.c b/drivers/media/usb/b2c2/flexcop-usb.c
> > index 7835bb0f32fc..eb54bfdda01f 100644
> > --- a/drivers/media/usb/b2c2/flexcop-usb.c
> > +++ b/drivers/media/usb/b2c2/flexcop-usb.c
> > @@ -509,7 +509,7 @@ static int flexcop_usb_init(struct flexcop_usb *fc_usb)
> >               return ret;
> >       }
> >
> > -     if (fc_usb->uintf->cur_altsetting->desc.bNumEndpoints < 1)
> > +     if (fc_usb->uintf->cur_altsetting->desc.bNumEndpoints < 2)
> >               return -ENODEV;
> >       if (!usb_endpoint_is_isoc_in(&fc_usb->uintf->cur_altsetting->endpoint[1].desc))
> >               return -ENODEV;
>
> It looks like it should have verified the type of endpoint[0] here
> instead.

This sanity check originally makes sure the
fc_usb->uintf->cur_altsetting->endpoint[0] in
flexcop_usb_transfer_init.

>
> Oliver?
>
> Johan