Re: [PATCH] linux/bitmap.h: fix BITMAP_LAST_WORD_MASK

From: Wei Wang
Date: Thu Jul 26 2018 - 06:04:49 EST

On 07/26/2018 04:48 PM, Andy Shevchenko wrote:
On Thu, Jul 26, 2018 at 11:07 AM, Wei Wang <> wrote:
The existing BITMAP_LAST_WORD_MASK macro returns 0xffffffff if nbits is
0. This patch changes the macro to return 0 when there is no bit needs to
be masked.

Can you provide a practical example of what's going wrong before this
patch applied?

The reason of making this patch is that I saw some other software which ports this function and has possibilities to fall into bugs with usages which pass 0 to the macro. So I wonder if it would be necessary to make such changes in case we would get a similar bug. Or adding something to explain that "0" is not applicable to this macro as a reminder to people who would use it.