linux-kernel - [PATCH] pinctrl: sunxi: fix use-after-free in sunxi_pmx

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Date:   Tue, 19 Jan 2021 14:29:08 +0800
From:   Liu Xiang <liu.xiang@...ngsmart.com>
To:     linux-gpio@...r.kernel.org
Cc:     linus.walleij@...aro.org, mripard@...nel.org, wens@...e.org,
        jernej.skrabec@...l.net, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, liuxiang_1999@....com,
        Liu Xiang <liu.xiang@...ngsmart.com>
Subject: [PATCH] pinctrl: sunxi: fix use-after-free in sunxi_pmx_free()

When CONFIG_REGULATOR is not set, sunxi_pmx_request() always return
success. Even a group of pins call sunxi_pmx_request(), the refcount
is only 1. This can cause a use-after-free warning in sunxi_pmx_free().
To solve this problem, go to err path if regulator_get() return NULL
or error.

Signed-off-by: Liu Xiang <liu.xiang@...ngsmart.com>
---
 drivers/pinctrl/sunxi/pinctrl-sunxi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/sunxi/pinctrl-sunxi.c b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
index dc8d39ae0..d1a8974eb 100644
--- a/drivers/pinctrl/sunxi/pinctrl-sunxi.c
+++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
@@ -777,7 +777,7 @@ static int sunxi_pmx_request(struct pinctrl_dev *pctldev, unsigned offset)
 
 	snprintf(supply, sizeof(supply), "vcc-p%c", 'a' + bank);
 	reg = regulator_get(pctl->dev, supply);
-	if (IS_ERR(reg)) {
+	if (IS_ERR_OR_NULL(reg)) {
 		dev_err(pctl->dev, "Couldn't get bank P%c regulator\n",
 			'A' + bank);
 		return PTR_ERR(reg);
@@ -811,7 +811,7 @@ static int sunxi_pmx_free(struct pinctrl_dev *pctldev, unsigned offset)
 					    PINS_PER_BANK;
 	struct sunxi_pinctrl_regulator *s_reg = &pctl->regulators[bank_offset];
 
-	if (!refcount_dec_and_test(&s_reg->refcount))
+	if (!s_reg->regulator || !refcount_dec_and_test(&s_reg->refcount))
 		return 0;
 
 	regulator_disable(s_reg->regulator);
-- 
2.17.1