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mdio-mux-gpio: Remove VLA usage

PATCH Superseded Kees Cook 2 participants 3 messages Jun 25, 2018

Subsystems (3)
Networking Network drivers Ethernet PHY

v3 of 4 Superseded Latest is v4 →

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Kees Cook

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#0 lore raw

PATCH v3 1/1 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 <[email protected]>
Reviewed-by Andrew Lunn <[email protected]>

---
v2: allocate array as part of structure (Andrew Lunn)
v3: resend to netdev with Reviewed-by

---
 drivers/net/phy/mdio-mux-gpio.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)
drivers/net/phy/mdio-mux-gpio.c +14 -8
index 082ffef0dec4..6b55e0ddef63 100644
@@ -20,23 +20,23 @@
 struct mdio_mux_gpio_state {
 	struct gpio_descs *gpios;
 	void *mux_handle;
+	int values[];
 };
 
 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];
 	unsigned int n;
 
 	if (current_child == desired_child)
 		return 0;
 
 	for (n = 0; n < s->gpios->ndescs; n++)
-		values[n] = (desired_child >> n) & 1;
+		s->values[n] = (desired_child >> n) & 1;
 
 	gpiod_set_array_value_cansleep(s->gpios->ndescs, s->gpios->desc,
-				       values);
+				       s->values);
 
 	return 0;
 }

@@ -44,15 +44,21 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child,
 static int mdio_mux_gpio_probe(struct platform_device *pdev)
 {
 	struct mdio_mux_gpio_state *s;
+	struct gpio_descs *gpios;
 	int r;
 
-	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
-	if (!s)
+	gpios = gpiod_get_array(&pdev->dev, NULL, GPIOD_OUT_LOW);
+	if (IS_ERR(gpios))
+		return PTR_ERR(gpios);
+
+	s = devm_kzalloc(&pdev->dev, sizeof(*s->values) * gpios->ndescs +
+				     sizeof(*s), GFP_KERNEL);
+	if (!s) {
+		gpiod_put_array(gpios);
 		return -ENOMEM;
+	}
 
-	s->gpios = gpiod_get_array(&pdev->dev, NULL, GPIOD_OUT_LOW);
-	if (IS_ERR(s->gpios))
-		return PTR_ERR(s->gpios);
+	s->gpios = gpios;
 
 	r = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
 			  mdio_mux_gpio_switch_fn, &s->mux_handle, s, NULL);
Signature · 6 lines
2.17.1


-- 
Kees Cook
Pixel Security
#1 lore raw
Quoted 3 lines · Kees Cook

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.

[]

drivers/net/phy/mdio-mux-gpio.c

Quoted 1 line
drivers/net/phy/mdio-mux-gpio.c +0 -0

[]

drivers/net/phy/mdio-mux-gpio.c static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, · line 45

Quoted 3 lines
drivers/net/phy/mdio-mux-gpio.c +0 -0
@@ -44,15 +44,21 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child,
 static int mdio_mux_gpio_probe(struct platform_device *pdev)
 {

[]

drivers/net/phy/mdio-mux-gpio.c static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, · line 55

Quoted 2 lines
drivers/net/phy/mdio-mux-gpio.c +2 -0
+	s = devm_kzalloc(&pdev->dev, sizeof(*s->values) * gpios->ndescs +
+				     sizeof(*s), GFP_KERNEL);

Isn't this supposed to use your new struct_size()

author
#2 lore raw
Quoted 9 lines · Joe Perches
Quoted 3 lines · Kees Cook

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.

[]

drivers/net/phy/mdio-mux-gpio.c

Quoted 1 line
drivers/net/phy/mdio-mux-gpio.c +0 -0

[]

Quoted 8 lines

drivers/net/phy/mdio-mux-gpio.c static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, · line 45

Quoted 3 lines
drivers/net/phy/mdio-mux-gpio.c +0 -0
@@ -44,15 +44,21 @@ static int mdio_mux_gpio_switch_fn(int current_child, int desired_child,
 static int mdio_mux_gpio_probe(struct platform_device *pdev)
 {

[]

drivers/net/phy/mdio-mux-gpio.c static int mdio_mux_gpio_switch_fn(int current_child, int desired_child, · line 55

Quoted 2 lines
drivers/net/phy/mdio-mux-gpio.c +2 -0
+     s = devm_kzalloc(&pdev->dev, sizeof(*s->values) * gpios->ndescs +
+                                  sizeof(*s), GFP_KERNEL);

Isn't this supposed to use your new struct_size()

Why yes. Yes it is. :) When treewide changes meet in the night! :) I'll send a v4.

-Kees

Signature · 2 lines
Kees Cook
Pixel Security