Re: [PATCH 4/5] idr: Handle integer overflow correctly

[Matthew Wilcox]

On Sun, Nov 03, 2019 at 03:40:11AM -0800, Matthew Wilcox wrote:
> If there is an entry at INT_MAX then idr_for_each_entry() will increment
> id after handling it.  This is undefined behaviour, and is caught by
> UBSAN.  Adding 1U to id forces the operation to be carried out as an
> unsigned addition which (when assigned to id) will result in INT_MIN.
> Since there is never an entry stored at INT_MIN, idr_get_next() will
> return NULL, ending the loop as expected.

This was an earlier version which got left around in the git format-patch
directory.  Please ignore.