[PATCH 6.1 65/73] gpio: prevent potential speculation leaks in gpio_device_get_desc()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hagar Hemdan <hagarhem@amazon.com>

commit d795848ecce24a75dfd46481aee066ae6fe39775 upstream.

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>
Link: https://lore.kernel.org/r/20240523085332.1801-1-hagarhem@amazon.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Hugo SIMELIERE <hsimeliere.opensource@witekio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpio/gpiolib.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -5,6 +5,7 @@
 #include <linux/module.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
+#include <linux/nospec.h>
 #include <linux/spinlock.h>
 #include <linux/list.h>
 #include <linux/device.h>
@@ -146,7 +147,7 @@ struct gpio_desc *gpiochip_get_desc(stru
 	if (hwnum >= gdev->ngpio)
 		return ERR_PTR(-EINVAL);
 
-	return &gdev->descs[hwnum];
+	return &gdev->descs[array_index_nospec(hwnum, gdev->ngpio)];
 }
 EXPORT_SYMBOL_GPL(gpiochip_get_desc);