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authorPeter Xu <peterx@redhat.com>2024-04-06 01:19:20 +0200
committerAndrew Morton <akpm@linux-foundation.org>2024-04-17 00:39:50 +0200
commitc5977c95dff182d6ee06f4d6f60bcb0284912969 (patch)
tree6548615dba04c524a87a760ac654d81ff70f7c97 /mm/hugetlb.c
parentmm,page_owner: fix printing of stack records (diff)
downloadlinux-c5977c95dff182d6ee06f4d6f60bcb0284912969.tar.xz
linux-c5977c95dff182d6ee06f4d6f60bcb0284912969.zip
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>
Diffstat (limited to '')
-rw-r--r--mm/hugetlb.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 23ef240ba48a..31d00eee028f 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)) {