[PATCH v4] gpio: prevent potential speculation leaks in gpio_device_get_desc()

[PATCH v4] gpio: prevent potential speculation leaks in gpio_device_get_desc()

[Hagar Hemdan]

Userspace may trigger a speculative read of an address outside the gpio
descriptor array.
Users can do that by calling gpio_ioctl() with an offset out of range.
Offset is copied from user and then used as an array index to get
the gpio descriptor without sanitization in gpio_device_get_desc().

This change ensures that the offset is sanitized by using
array_index_nospec() to mitigate any possibility of speculative
information leaks.

This bug was discovered and resolved using Coverity Static Analysis
Security Testing (SAST) by Synopsys, Inc.

Signed-off-by: Hagar Hemdan <hagarhem@amazon.com>
---
v4: removed Fixes commit.
---
 drivers/gpio/gpiolib.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index fa62367ee929..1a9aadd4c803 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -17,6 +17,7 @@
 #include <linux/list.h>
 #include <linux/lockdep.h>
 #include <linux/module.h>
+#include <linux/nospec.h>
 #include <linux/of.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/seq_file.h>
@@ -198,7 +199,7 @@ gpio_device_get_desc(struct gpio_device *gdev, unsigned int hwnum)
 	if (hwnum >= gdev->ngpio)
 		return ERR_PTR(-EINVAL);
 
-	return &gdev->descs[hwnum];
+	return &gdev->descs[array_index_nospec(hwnum, gdev->ngpio)];
 }
 EXPORT_SYMBOL_GPL(gpio_device_get_desc);
 
-- 
2.40.1

Re: [PATCH v4] gpio: prevent potential speculation leaks in gpio_device_get_desc()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>


On Thu, 23 May 2024 08:53:32 +0000, Hagar Hemdan wrote:
> Userspace may trigger a speculative read of an address outside the gpio
> descriptor array.
> Users can do that by calling gpio_ioctl() with an offset out of range.
> Offset is copied from user and then used as an array index to get
> the gpio descriptor without sanitization in gpio_device_get_desc().
> 
> This change ensures that the offset is sanitized by using
> array_index_nospec() to mitigate any possibility of speculative
> information leaks.
> 
> [...]

Applied, thanks!

[1/1] gpio: prevent potential speculation leaks in gpio_device_get_desc()
      commit: d795848ecce24a75dfd46481aee066ae6fe39775

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@linaro.org>