Re: [PATCH][next] gpio: xilinx: Fix potential integer overflow on shift of a u32 int

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Thu, May 13, 2021 at 12:12 PM Colin King <colin.king@xxxxxxxxxxxxx> wrote:
>
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> The left shift of the u32 integer v is evaluated using 32 bit
> arithmetic and then assigned to a u64 integer. There are cases
> where v will currently overflow on the shift. Avoid this by
> casting it to unsigned long (same type as map[]) before shifting
> it.
>
> Addresses-Coverity: ("Unintentional integer overflow")
> Fixes: 02b3f84d9080 ("gpio: xilinx: Switch to use bitmap APIs")

No, it is a false positive,

>         const unsigned long offset = (bit % BITS_PER_LONG) & BIT(5);

See above, offset is 0 when BITS_PER_LONG == 32 and 32 when it's equal to 64.

> -       map[index] |= v << offset;
> +       map[index] |= (unsigned long)v << offset;

-- 
With Best Regards,
Andy Shevchenko