linux-kernel - Re: [Linux-kernel-mentees] [PATCH v3] media/v4l2-core: Fix kernel-infoleak in video_put

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Date:   Thu, 30 Jul 2020 10:07:13 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Peilin Ye <yepeilin.cs@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Vandana BN <bnvandana@...il.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [Linux-kernel-mentees] [PATCH v3] media/v4l2-core: Fix
 kernel-infoleak in video_put_user()

On Tue, Jul 28, 2020 at 3:58 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Tue, Jul 28, 2020 at 3:06 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> >
> > On Tue, Jul 28, 2020 at 02:22:29PM +0200, Linus Walleij wrote:
> > > On Mon, Jul 27, 2020 at 3:17 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > >
> > > > Here are my latest warnings on linux-next from Friday.
> > >
> > > Thanks for sharing this Dan, very interesting findings.
> > >
> > > > drivers/gpio/gpiolib-cdev.c:473 lineevent_read() warn: check that 'ge' doesn't leak information (struct has a hole after 'id')
> > >
> > > We are revamping the ABI for 64bit compatibility so we are now running
> > > pahole on our stuff. I suppose we need to think about mending this old ABI
> > > as well.
> >
> > Yeah...  But this one is a false positive.  It's not super hard for me
> > to silence it actually.  I'll take care of it.  It could be a while
> > before I push this to the public repository though...
>
> The lineevent_read() function still needs to be fixed to support
> 32-bit compat mode on x86, which is independent of the warning.
>
> Something like
>
> static int lineevent_put_data(void __user *uptr, struct gpioevent_data *ge)
> {
> #ifdef __x86_64__
>         /* i386 has no padding after 'id' */
>         if (in_ia32_syscall()) {
>                 struct {
>                         compat_u64      timestamp __packed;
>                         u32             id;
>                 } compat_ge = { ge->timestamp, ge->id };
>
>                 if (copy_to_user(uptr, &compat_ge, sizeof(compat_ge)))
>                         return -EFAULT;
>
>                 return sizeof(compat_ge);
>         }
> #endif
>
>         if (copy_to_user(uptr, ge, sizeof(*ge))
>                 return -EFAULT;
>
>         return sizeof(*ge);
> }
>
>        Arnd

Hi Arnd,

Andy actually had a patch for that but since this isn't a regression
(it never worked), we decided to leave it as it is and get it right in
v2 API.

Bartosz