Re: [PATCH 2/2] userfaultfd: fix PTE unmapping stack-allocated PTE copies

[Peter Xu]

On Wed, Feb 26, 2025 at 10:55:09AM -0800, Suren Baghdasaryan wrote:
> Current implementation of move_pages_pte() copies source and destination
> PTEs in order to detect concurrent changes to PTEs involved in the move.
> However these copies are also used to unmap the PTEs, which will fail if
> CONFIG_HIGHPTE is enabled because the copies are allocated on the stack.
> Fix this by using the actual PTEs which were kmap()ed.
> 
> Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
> Reported-by: Peter Xu <peterx@xxxxxxxxxx>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>

-- 
Peter Xu