Re: [Linux-kernel-mentees] [PATCH v3] media/v4l2-core: Fix kernel-infoleak in video_put_user()

Bartosz Golaszewski
2020-07-30T08:20:03Z

On Tue, Jul 28, 2020 at 3:58 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Tue, Jul 28, 2020 at 3:06 PM Dan Carpenter <dan.carpenter@oracle.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@oracle.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