linux-kernel - Re: [PATCH] HID: wacom: avoid integer overflow in wacom_intuos

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Message-ID: <CAF8JNh+Ba1SNT5JFy3EGAAtcfZdRYcQ_M4LtQoV0H0dViFyGcw@mail.gmail.com>
Date:   Mon, 17 Apr 2023 10:13:43 -0700
From:   Ping Cheng <pinglinux@...il.com>
To:     Nikita Zhandarovich <n.zhandarovich@...tech.ru>
Cc:     Ping Cheng <ping.cheng@...om.com>,
        Jason Gerecke <jason.gerecke@...om.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH] HID: wacom: avoid integer overflow in wacom_intuos_inout()

On Mon, Apr 17, 2023 at 9:03 AM Nikita Zhandarovich
<n.zhandarovich@...tech.ru> wrote:
>
> If high bit is set to 1 in ((data[3] & 0x0f << 28), after all arithmetic
> operations and integer promotions are done, high bits in
> wacom->serial[idx] will be filled with 1s as well.
> Avoid this, albeit unlikely, issue by specifying left operand's __u64
> type for the right operand.

Thank you Nikita for the fix! It's good to avoid potential issues.

> Found by Linux Verification Center (linuxtesting.org) with static
> analysis tool SVACE.
>
> Fixes: 3bea733ab212 ("USB: wacom tablet driver reorganization")
> Signed-off-by: Nikita Zhandarovich <n.zhandarovich@...tech.ru>

Reviewed-by: Ping Cheng <ping.cheng@...om.com>
Cc: stable@...r.kernel.org

Cheers,
Ping
> ---
>  drivers/hid/wacom_wac.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
> index 9312d611db8e..0e4404f3801e 100644
> --- a/drivers/hid/wacom_wac.c
> +++ b/drivers/hid/wacom_wac.c
> @@ -826,7 +826,7 @@ static int wacom_intuos_inout(struct wacom_wac *wacom)
>         /* Enter report */
>         if ((data[1] & 0xfc) == 0xc0) {
>                 /* serial number of the tool */
> -               wacom->serial[idx] = ((data[3] & 0x0f) << 28) +
> +               wacom->serial[idx] = ((__u64)(data[3] & 0x0f) << 28) +
>                         (data[4] << 20) + (data[5] << 12) +
>                         (data[6] << 4) + (data[7] >> 4);
>
> --
> 2.25.1
>