linux-kernel - [PATCH] gpiolib: never report open-drain/source lines as 'input' to user-space

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Tue,  6 Aug 2019 13:41:51 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        stable <stable@...r.kernel.org>
Subject: [PATCH] gpiolib: never report open-drain/source lines as 'input' to user-space

From: Bartosz Golaszewski <bgolaszewski@...libre.com>

If the driver doesn't support open-drain/source config options, we
emulate this behavior when setting the direction by calling
gpiod_direction_input() if the default value is 0 (open-source) or
1 (open-drain), thus not actively driving the line in those cases.

This however clears the FLAG_IS_OUT bit for the GPIO line descriptor
and makes the LINEINFO ioctl() incorrectly report this line's mode as
'input' to user-space.

This commit modifies the ioctl() to always set the GPIOLINE_FLAG_IS_OUT
bit in the lineinfo structure's flags field. Since it's impossible to
use the input mode and open-drain/source options at the same time, we
can be sure the reported information will be correct.

Fixes: 521a2ad6f862 ("gpio: add userspace ABI for GPIO line information")
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
---
 drivers/gpio/gpiolib.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f497003f119c..80a2a2cb673b 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1091,9 +1091,11 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
 			lineinfo.flags |= GPIOLINE_FLAG_ACTIVE_LOW;
 		if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_OPEN_DRAIN;
+			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_DRAIN |
+					   GPIOLINE_FLAG_IS_OUT);
 		if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_OPEN_SOURCE;
+			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
+					   GPIOLINE_FLAG_IS_OUT);

 		if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
 			return -EFAULT;
-- 
2.21.0