From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Bartosz Golaszewski , Linus Walleij , Sasha Levin Subject: [PATCH AUTOSEL 4.18 34/92] gpiolib: don't allow userspace to set values of input lines Date: Sat, 15 Sep 2018 01:30:13 +0000 Message-ID: <20180915012944.179481-34-alexander.levin@microsoft.com> References: <20180915012944.179481-1-alexander.levin@microsoft.com> In-Reply-To: <20180915012944.179481-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: From: Bartosz Golaszewski [ 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 Signed-off-by: Linus Walleij Signed-off-by: Sasha Levin --- drivers/gpio/gpiolib.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index e11a3bb03820..57973524360d 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -449,7 +449,13 @@ static long linehandle_ioctl(struct file *filep, unsig= ned int cmd, =20 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 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; =20 --=20 2.17.1