mm/uffd: fix vma check on userfault for wp

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
b1f9e876862d when moving code around.  Fix it.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: b1f9e876862d ("mm/uffd: enable write protection for shmem & hugetlbfs")
Signed-off-by: Peter Xu <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions