linux-kernel - [PATCH] gpiolib: don't check the retval of get

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]

Message-ID: <20250311175631.83779-1-brgl@bgdev.pl>
Date: Tue, 11 Mar 2025 18:56:31 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>,
	Genes Lists <lists@...ience.com>
Cc: linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH] gpiolib: don't check the retval of get_direction() when registering a chip

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

During chip registration we should neither check the return value of
gc->get_direction() nor hold the SRCU lock when calling it. The former
is because pin controllers may have pins set to alternate functions and
return errors from their get_direction() callbacks. That's alright - we
should default to the safe INPUT state and not bail-out. The latter is
not needed because we haven't registered the chip yet so there's nothing
to protect against dynamic removal. In fact: we currently hit a lockdep
splat. Revert to calling the gc->get_direction() callback directly and
*not* checking its value.

Fixes: 9d846b1aebbe ("gpiolib: check the return value of gpio_chip::get_direction()")
Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Closes: https://lore.kernel.org/all/81f890fc-6688-42f0-9756-567efc8bb97a@samsung.com/
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
Link: https://lore.kernel.org/r/20250226-retval-fixes-v2-1-c8dc57182441@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
This commit is in linux-next as 9becde08f1bc ("gpiolib: don't use
gpiochip_get_direction() when registering a chip") and was applied as
a fix to commits e623c4303ed1 ("gpiolib: sanitize the return value of
gpio_chip::get_direction()") and 9d846b1aebbe ("gpiolib: check the return
value of gpio_chip::get_direction()"). Becuase the former is queued for
v6.15-rc1, this fix was never applied to v6.14 and sent upstream.

However, the warning it addresses is now queued for v6.14. I've rebased
this commit on top of v6.14-rc6 and would like to send it upstream. Once
merged, I'll pull v6.14-rc7 back into my for-next branch and fix the
conflicts.

 drivers/gpio/gpiolib.c | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 8741600af7ef..de708d081858 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1056,24 +1056,19 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 
 		desc->gdev = gdev;
 
-		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index)) {
-			ret = gc->get_direction(gc, desc_index);
-			if (ret < 0)
-				/*
-				 * FIXME: Bail-out here once all GPIO drivers
-				 * are updated to not return errors in
-				 * situations that can be considered normal
-				 * operation.
-				 */
-				dev_warn(&gdev->dev,
-					 "%s: get_direction failed: %d\n",
-					 __func__, ret);
-
-			assign_bit(FLAG_IS_OUT, &desc->flags, !ret);
-		} else {
+		/*
+		 * We would typically want to check the return value of
+		 * get_direction() here but we must not check the return value
+		 * and bail-out as pin controllers can have pins configured to
+		 * alternate functions and return -EINVAL. Also: there's no
+		 * need to take the SRCU lock here.
+		 */
+		if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index))
+			assign_bit(FLAG_IS_OUT, &desc->flags,
+				   !gc->get_direction(gc, desc_index));
+		else
 			assign_bit(FLAG_IS_OUT,
 				   &desc->flags, !gc->direction_input);
-		}
 	}
 
 	ret = of_gpiochip_add(gc);
-- 
2.45.2