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From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Mon, 24 Sep 2018 14:57:38 +0200
Message-ID: <CAMRc=Mc92mF18Tax+6hPdAYnw4t4_pD3FjVOGAzxttJCRP5gdA@mail.gmail.com>
Subject: Re: [PATCH 4.18 177/235] gpiolib: dont allow userspace to set values
 of input lines
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        stable <stable@vger.kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        alexander.levin@microsoft.com
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pon., 24 wrz 2018 o 14:41 Greg Kroah-Hartman
<gregkh@linuxfoundation.org> napisa=C5=82(a):
>
> 4.18-stable review patch.  If anyone has any objections, please let me kn=
ow.
>
> ------------------
>
> From: Bartosz Golaszewski <brgl@bgdev.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@bgdev.pl>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 =3D=3D GPIOHANDLE_SET_LINE_VALUES_IOCTL) {
> -               /* TODO: check if descriptors are really output */
> +               /*
> +                * All line descriptors were created at once with the sam=
e
> +                * 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

Best regards,
Bartosz Golaszewski