linux-kernel - [PATCH] mdio-mux-gpio: Remove VLA usage

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Date:   Tue, 29 May 2018 15:59:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Pramod Kumar <pramod.kumar@...adcom.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] mdio-mux-gpio: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
allocates the values buffer during the callback instead of putting it
on the stack.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/net/phy/mdio-mux-gpio.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/mdio-mux-gpio.c b/drivers/net/phy/mdio-mux-gpio.c
index 082ffef0dec4..e99994f4ed50 100644
--- a/drivers/net/phy/mdio-mux-gpio.c
+++ b/drivers/net/phy/mdio-mux-gpio.c
@@ -26,18 +26,23 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child,
 				   void *data)
 {
 	struct mdio_mux_gpio_state *s = data;
-	int values[s->gpios->ndescs];
+	int *values;
 	unsigned int n;
 
 	if (current_child == desired_child)
 		return 0;
 
+	values = kmalloc_array(s->gpios->ndescs, sizeof(*values), GFP_KERNEL);
+	if (!values)
+		return -ENOMEM;
+
 	for (n = 0; n < s->gpios->ndescs; n++)
 		values[n] = (desired_child >> n) & 1;
 
 	gpiod_set_array_value_cansleep(s->gpios->ndescs, s->gpios->desc,
 				       values);
 
+	kfree(values);
 	return 0;
 }
 
-- 
2.17.0


-- 
Kees Cook
Pixel Security