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

On Thu, May 13, 2021 at 12:12 PM Colin King [off-list ref] wrote:

From: Colin Ian King <redacted>

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