linux-kernel - [PATCH] Input: uinput - fix undefined behavior in uinput_validate

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Date:   Mon, 14 Jan 2019 14:04:48 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     linux-input@...r.kernel.org
Cc:     Byoungyoung Lee <lifeasageek@...il.com>, rydberg@...math.org,
        DaeRyong Jeong <threeearcat@...il.com>,
        syzkaller@...glegroups.com,
        Peter Hutterer <peter.hutterer@...-t.net>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Input: uinput - fix undefined behavior in
 uinput_validate_absinfo()

An integer overflow may arise in uinput_validate_absinfo() if "max - min"
can't be represented by an "int". We should check for overflow before
trying to use the result.

Reported-by: Kyungtae Kim <kt0755@...il.com>
Cc: stable@...r.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/input/misc/uinput.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 8ec483e8688b..26ec603fe220 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -39,6 +39,7 @@
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/miscdevice.h>
+#include <linux/overflow.h>
 #include <linux/input/mt.h>
 #include "../input-compat.h"
 
@@ -405,7 +406,7 @@ static int uinput_open(struct inode *inode, struct file *file)
 static int uinput_validate_absinfo(struct input_dev *dev, unsigned int code,
 				   const struct input_absinfo *abs)
 {
-	int min, max;
+	int min, max, range;
 
 	min = abs->minimum;
 	max = abs->maximum;
@@ -417,7 +418,7 @@ static int uinput_validate_absinfo(struct input_dev *dev, unsigned int code,
 		return -EINVAL;
 	}
 
-	if (abs->flat > max - min) {
+	if (check_sub_overflow(max, min, &range) && abs->flat > range) {
 		printk(KERN_DEBUG
 		       "%s: abs_flat #%02x out of range: %d (min:%d/max:%d)\n",
 		       UINPUT_NAME, code, abs->flat, min, max);
-- 
2.20.1.97.g81188d93c3-goog


-- 
Dmitry