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Subject: Re: [PATCH][next] platform/surface: fix potential integer overflow on
 shift of a int
To:     Colin King <colin.king@canonical.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Mark Gross <mgross@linux.intel.com>,
        platform-driver-x86@vger.kernel.org
Cc:     kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210111144648.20498-1-colin.king@canonical.com>
From:   Maximilian Luz <luzmaximilian@gmail.com>
Message-ID: <94d4044a-d50f-0108-9312-53338c388f39@gmail.com>
Date:   Mon, 11 Jan 2021 16:03:56 +0100
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On 1/11/21 3:46 PM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The left shift of int 32 bit integer constant 1 is evaluated using 32 bit
> arithmetic and then passed as a 64 bit function argument. In the case where
> func is 32 or more this can lead to an oveflow.  Avoid this by shifting
> using the BIT_ULL macro instead.
> 
> Addresses-Coverity: ("Unintentional integer overflow")
> Fixes: fc00bc8ac1da ("platform/surface: Add Surface ACPI Notify driver")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>   drivers/platform/surface/surface_acpi_notify.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/surface/surface_acpi_notify.c b/drivers/platform/surface/surface_acpi_notify.c
> index 8cd67a669c86..ef9c1f8e8336 100644
> --- a/drivers/platform/surface/surface_acpi_notify.c
> +++ b/drivers/platform/surface/surface_acpi_notify.c
> @@ -188,7 +188,7 @@ static int san_acpi_notify_event(struct device *dev, u64 func,
>   	union acpi_object *obj;
>   	int status = 0;
>   
> -	if (!acpi_check_dsm(san, &SAN_DSM_UUID, SAN_DSM_REVISION, 1 << func))
> +	if (!acpi_check_dsm(san, &SAN_DSM_UUID, SAN_DSM_REVISION, BIT_ULL(func)))
>   		return 0;
>   
>   	dev_dbg(dev, "notify event %#04llx\n", func);
> 

Thanks, looks good to me.

Reviewed-by: Maximilian Luz <luzmaximilian@gmail.com>

Regards,
Max