Re: [PATCH v4 08/14] userfaultfd: add UFFDIO_REGISTER_MODE_RWP and UFFDIO_RWPROTECT plumbing

[Kiryl Shutsemau]

On Mon, May 25, 2026 at 04:19:43PM +0100, Kiryl Shutsemau wrote:
> On Mon, May 25, 2026 at 12:11:11PM +0000, sashiko-bot@xxxxxxxxxx wrote:
> > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> > 
> > Pre-existing issues:
> > - [High] Page tables are accessed and modified under mmap_write_lock
> > without first draining per-VMA lock holders via vma_start_write(),
> > risking races with concurrent per-VMA readers.
> 
> Confirmed and pre-existing -- the pre-patch path called uffd_wp_range()
> which has the same gap (no vma_start_write() before change_protection()
> either). Will address in a follow-up that audits the userfaultfd
> register/unregister paths together.

Looking again, this is false alarm. PTL provides enough serialization
here. No change needed.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov