linux-kernel - [PATCH 5.18 0777/1095] gpio: gpiolib-of: Fix refcount bugs in of_mm_gpiochip_add

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Message-Id: <20220815180501.410976577@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 20:02:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Liang He <windhl@....com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 0777/1095] gpio: gpiolib-of: Fix refcount bugs in of_mm_gpiochip_add_data()

From: Liang He <windhl@....com>

[ Upstream commit 5d07a692f9562f9c06e62cce369e9dd108173a0f ]

We should use of_node_get() when a new reference of device_node
is created. It is noted that the old reference stored in
'mm_gc->gc.of_node' should also be decreased.

This patch is based on the fact that there is a call site in function
'qe_add_gpiochips()' of src file 'drivers\soc\fsl\qe\gpio.c'. In this
function, of_mm_gpiochip_add_data() is contained in an iteration of
for_each_compatible_node() which will automatically increase and
decrease the refcount. So we need additional of_node_get() for the
reference escape in of_mm_gpiochip_add_data().

Fixes: a19e3da5bc5f ("of/gpio: Kill of_gpio_chip and add members directly to gpio_chip")
Signed-off-by: Liang He <windhl@....com>
Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpio/gpiolib-of.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 6dec81b1f24b..5cabb9a9c272 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -861,7 +861,8 @@ int of_mm_gpiochip_add_data(struct device_node *np,
 	if (mm_gc->save_regs)
 		mm_gc->save_regs(mm_gc);
 
-	mm_gc->gc.of_node = np;
+	of_node_put(mm_gc->gc.of_node);
+	mm_gc->gc.of_node = of_node_get(np);
 
 	ret = gpiochip_add_data(gc, data);
 	if (ret)
@@ -869,6 +870,7 @@ int of_mm_gpiochip_add_data(struct device_node *np,
 
 	return 0;
 err2:
+	of_node_put(np);
 	iounmap(mm_gc->regs);
 err1:
 	kfree(gc->label);
-- 
2.35.1