linux-kernel - [PATCH] pinctrl: fix deadlock in create_pinctrl() when handling -EPROBE

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Message-ID: <20240604071901.3343-1-hagarhem@amazon.com>
Date: Tue, 4 Jun 2024 07:19:01 +0000
From: Hagar Hemdan <hagarhem@...zon.com>
To:
CC: Maximilian Heyne <mheyne@...zon.de>, Norbert Manthey <nmanthey@...zon.de>,
	Hagar Hemdan <hagarhem@...zon.com>, Linus Walleij <linus.walleij@...aro.org>,
	Patrice Chotard <patrice.chotard@...com>, <linux-gpio@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] pinctrl: fix deadlock in create_pinctrl() when handling -EPROBE_DEFER

In create_pinctrl(), pinctrl_maps_mutex is acquired before calling
add_setting(). If add_setting() returns -EPROBE_DEFER, create_pinctrl()
calls pinctrl_free(). However, pinctrl_free() attempts to acquire
pinctrl_maps_mutex, which is already held by create_pinctrl(), leading to
a potential deadlock.

This patch resolves the issue by releasing pinctrl_maps_mutex before
calling pinctrl_free(), preventing the deadlock.

Fixes: 42fed7ba44e4 ("pinctrl: move subsystem mutex to pinctrl_dev struct")
Suggested-by: Maximilian Heyne <mheyne@...zon.de>
Signed-off-by: Hagar Hemdan <hagarhem@...zon.com>
---
Only compile-tested.
---
 drivers/pinctrl/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index ee56856cb80c..29d9ef535dbe 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1102,8 +1102,8 @@ static struct pinctrl *create_pinctrl(struct device *dev,
 		 * an -EPROBE_DEFER later, as that is the worst case.
 		 */
 		if (ret == -EPROBE_DEFER) {
-			pinctrl_free(p, false);
 			mutex_unlock(&pinctrl_maps_mutex);
+			pinctrl_free(p, false);
 			return ERR_PTR(ret);
 		}
 	}
-- 
2.40.1