linux-kernel - [PATCH v1 1/2] pinctrl: Duplicate user memory in one go in pinmux

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Message-Id: <20230604131215.78847-1-andriy.shevchenko@linux.intel.com>
Date:   Sun,  4 Jun 2023 16:12:14 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH v1 1/2] pinctrl: Duplicate user memory in one go in pinmux_select()

Current code is suboptimal in three ways:
1) it explicitly terminates the string which is not needed;
2) it might provoke additional faults, because asked lenght might be
   bigger than the real one;
3) it consumes more than needed lines in the source.

Instead of using kmalloc() + strncpy_from_user() + terminating, just
utilize memdup_user_nul().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 drivers/pinctrl/pinmux.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 021382632608..2d2f3bd164d5 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -692,14 +692,9 @@ static ssize_t pinmux_select(struct file *file, const char __user *user_buf,
 	if (len > PINMUX_SELECT_MAX)
 		return -ENOMEM;
 
-	buf = kzalloc(PINMUX_SELECT_MAX, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	ret = strncpy_from_user(buf, user_buf, PINMUX_SELECT_MAX);
-	if (ret < 0)
-		goto exit_free_buf;
-	buf[len-1] = '\0';
+	buf = memdup_user_nul(user_buf, len);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
 
 	/* remove leading and trailing spaces of input buffer */
 	gname = strstrip(buf);
-- 
2.40.0.1.gaa8946217a0b