2019-01-14 22:08:01

by Dmitry Torokhov

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 <[email protected]>
Cc: [email protected]
Signed-off-by: Dmitry Torokhov <[email protected]>
---
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

2019-01-14 22:09:39

by Dmitry Torokhov

Subject: Re: [PATCH] Input: uinput - fix undefined behavior in uinput_validate_absinfo()

On Mon, Jan 14, 2019 at 02:04:48PM -0800, Dmitry Torokhov wrote:
> 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 <[email protected]>
> Cc: [email protected]
> Signed-off-by: Dmitry Torokhov <[email protected]>
> ---
> 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) {

This should be !check_sub_overflow(...) of course.

> 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

--
Dmitry

2019-01-14 22:48:30

by Peter Hutterer

Subject: Re: [PATCH] Input: uinput - fix undefined behavior in uinput_validate_absinfo()

On Mon, Jan 14, 2019 at 02:07:56PM -0800, Dmitry Torokhov wrote:
> On Mon, Jan 14, 2019 at 02:04:48PM -0800, Dmitry Torokhov wrote:
> > 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 <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Dmitry Torokhov <[email protected]>
> > ---
> > 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) {
>
> This should be !check_sub_overflow(...) of course.

Reviewed-by: Peter Hutterer <[email protected]> with that in place,
thanks.

Cheers,
Peter


> > 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
>
> --
> Dmitry