linux-kernel - [PATCH v2] gpiolib: sysfs: Fix error handling on failed export

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: <20231128141321.51669-1-boerge.struempfel@gmail.com>
Date:   Tue, 28 Nov 2023 15:13:21 +0100
From:   Boerge Struempfel <boerge.struempfel@...il.com>
To:     andy@...nel.org, Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     boerge.struempfel@...il.com, bstruempfel@...ratronik.de
Subject: [PATCH v2] gpiolib: sysfs: Fix error handling on failed export

If gpio_set_transitory() fails, we should free the gpio again. Most
notably, the flag FLAG_REQUESTED has previously been set in
gpiod_request_commit(), and should be reset on failure.

To my knowledge, this does not affect any current users, since the
gpio_set_transitory() mainly returns 0 and -ENOTSUPP, which is converted
to 0. However the gpio_set_transitory() function calles the .set_config()
function of the corresponding gpio chip and there are some gpio drivers in
which some (unlikely) branches return other values like -EPROBE_DEFER,
and EINVAL. In these cases, the above mentioned FLAG_REQUESTED would not
be reset, which results in the pin being blocked until the next reboot.

Signed-off-by: Boerge Struempfel <boerge.struempfel@...il.com>

---

V1: https://lore.kernel.org/linux-gpio/CAEktqcuxS1sPfkGVCgSy1ki8fmUDmuUsHrdAT+zFKy5vGSoKPw@mail.gmail.com/T/#t

Changes from V1:
	- Marked all functions in commit message with parenthesis
	- Elaborated in commit message

 drivers/gpio/gpiolib-sysfs.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6f309a3b2d9a..12d853845bb8 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -474,14 +474,17 @@ static ssize_t export_store(const struct class *class,
 		goto done;

 	status = gpiod_set_transitory(desc, false);
-	if (!status) {
-		status = gpiod_export(desc, true);
-		if (status < 0)
-			gpiod_free(desc);
-		else
-			set_bit(FLAG_SYSFS, &desc->flags);
+	if (status) {
+		gpiod_free(desc);
+		goto done;
 	}

+	status = gpiod_export(desc, true);
+	if (status < 0)
+		gpiod_free(desc);
+	else
+		set_bit(FLAG_SYSFS, &desc->flags);
+
 done:
 	if (status)
 		pr_debug("%s: status %d\n", __func__, status);
-- 
2.42.0