We used to have a report that pte-marker code can be reached even when
uffd-wp is not compiled in for file memories, here:
https://lore.kernel.org/all/YzeR+R6b4bwBlBHh@x1n/T/#u
I just got time to revisit this and found that the root cause is we simply
messed up with the vma check, so that for !PTE_MARKER_UFFD_WP system, we
will allow UFFDIO_REGISTER of MINOR & WP upon shmem as the check was
wrong:
if (vm_flags & VM_UFFD_MINOR)
return is_vm_hugetlb_page(vma) || vma_is_shmem(vma);
Where we'll allow anything to pass on shmem as long as minor mode is
requested.
Axel did it right when introducing minor mode but I messed it up in
b1f9e87686 when moving code around. Fix it.
Link: https://lkml.kernel.org/r/20221024193336.1233616-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20221024193336.1233616-2-peterx@redhat.com
Fixes: b1f9e87686 ("mm/uffd: enable write protection for shmem & hugetlbfs")
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
67eae54bc2