linux-kernel - Re: [PATCH 4.18 177/235] gpiolib: dont allow userspace to set values of input lines

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Date:   Mon, 24 Sep 2018 20:06:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        alexander.levin@...rosoft.com
Subject: Re: [PATCH 4.18 177/235] gpiolib: dont allow userspace to set values
 of input lines

On Mon, Sep 24, 2018 at 02:57:38PM +0200, Bartosz Golaszewski wrote:
> pon., 24 wrz 2018 o 14:41 Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> napisał(a):
> >
> > 4.18-stable review patch.  If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Bartosz Golaszewski <brgl@...ev.pl>
> >
> > [ Upstream commit e5332d5437764f775cf4e3b8ca3bf592af063a02 ]
> >
> > User space can currently both read and set values of input lines using
> > the character device. This was not allowed by the old sysfs interface
> > nor is it a correct behavior.
> >
> > Check the first descriptor in the set for the OUT flag when asked to
> > set values and return -EPERM if the line is input.
> >
> > Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
> > Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
> > Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  drivers/gpio/gpiolib.c |    8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -449,7 +449,13 @@ static long linehandle_ioctl(struct file
> >
> >                 return 0;
> >         } else if (cmd == GPIOHANDLE_SET_LINE_VALUES_IOCTL) {
> > -               /* TODO: check if descriptors are really output */
> > +               /*
> > +                * All line descriptors were created at once with the same
> > +                * flags so just check if the first one is really output.
> > +                */
> > +               if (!test_bit(FLAG_IS_OUT, &lh->descs[0]->flags))
> > +                       return -EPERM;
> > +
> >                 if (copy_from_user(&ghd, ip, sizeof(ghd)))
> >                         return -EFAULT;
> >
> >
> >
> 
> Hi Greg,
> 
> FYI Linus suggested that we don't send this one for stable:
> https://lkml.org/lkml/2018/7/20/1065

Ok, that was hard to dig out.  This was sent as review last week.  I'll
go drop it, thanks for letting me know.

greg k-h