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From: Hagar Hemdan <hagarhem@amazon.com>
To:
CC: Norbert Manthey <nmanthey@amazon.de>, Hagar Hemdan <hagarhem@amazon.com>,
	Linus Walleij <linus.walleij@linaro.org>, Bartosz Golaszewski
	<brgl@bgdev.pl>, Kent Gibson <warthog618@gmail.com>,
	<linux-gpio@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: [PATCH v2] gpio: prevent potential speculation leaks in gpio_device_get_desc()
Date: Fri, 17 May 2024 09:09:04 +0000
Message-ID: <20240517090904.22812-1-hagarhem@amazon.com>
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Users can call the gpio_ioctl() interface to get information about gpio
chip lines.
Lines on the chip are identified by an offset in the range
of [0,chip.lines).
Offset is copied from user and then used as an array index to get
the gpio descriptor without sanitization.

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.

Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Signed-off-by: Hagar Hemdan <hagarhem@amazon.com>
---
v2: call array_index_nospec() after the bounds check. 
---
 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 fa50db0c3605..b58e4fe78cec 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>
@@ -201,7 +202,7 @@ 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