diff options
| author | Peter Xu <peterx@redhat.com> | 2024-04-05 19:19:20 -0400 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-04-16 15:39:50 -0700 |
| commit | c5977c95dff182d6ee06f4d6f60bcb0284912969 (patch) | |
| tree | 6548615dba04c524a87a760ac654d81ff70f7c97 | |
| parent | 74017458017127ca6bf14b1f9fda69e03f43389b (diff) | |
| download | linux-c5977c95dff182d6ee06f4d6f60bcb0284912969.tar.gz | |
mm/userfaultfd: allow hugetlb change protection upon poison entry
After UFFDIO_POISON, there can be two kinds of hugetlb pte markers, either
the POISON one or UFFD_WP one.
Allow change protection to run on a poisoned marker just like !hugetlb
cases, ignoring the marker irrelevant of the permission.
Here the two bits are mutual exclusive. For example, when install a
poisoned entry it must not be UFFD_WP already (by checking pte_none()
before such install). And it also means if UFFD_WP is set there must have
no POISON bit set. It makes sense because UFFD_WP is a bit to reflect
permission, and permissions do not apply if the pte is poisoned and
destined to sigbus.
So here we simply check uffd_wp bit set first, do nothing otherwise.
Attach the Fixes to UFFDIO_POISON work, as before that it should not be
possible to have poison entry for hugetlb (e.g., hugetlb doesn't do swap,
so no chance of swapin errors).
Link: https://lkml.kernel.org/r/20240405231920.1772199-1-peterx@redhat.com
Link: https://lore.kernel.org/r/000000000000920d5e0615602dd1@google.com
Fixes: fc71884a5f59 ("mm: userfaultfd: add new UFFDIO_POISON ioctl")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: syzbot+b07c8ac8eee3d4d8440f@syzkaller.appspotmail.com
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: <stable@vger.kernel.org> [6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/hugetlb.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 23ef240ba48a60..31d00eee028f11 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7044,9 +7044,13 @@ long hugetlb_change_protection(struct vm_area_struct *vma, if (!pte_same(pte, newpte)) set_huge_pte_at(mm, address, ptep, newpte, psize); } else if (unlikely(is_pte_marker(pte))) { - /* No other markers apply for now. */ - WARN_ON_ONCE(!pte_marker_uffd_wp(pte)); - if (uffd_wp_resolve) + /* + * Do nothing on a poison marker; page is + * corrupted, permissons do not apply. Here + * pte_marker_uffd_wp()==true implies !poison + * because they're mutual exclusive. + */ + if (pte_marker_uffd_wp(pte) && uffd_wp_resolve) /* Safe to modify directly (non-present->none). */ huge_pte_clear(mm, address, ptep, psize); } else if (!huge_pte_none(pte)) { |