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mm/hugetlb: tolerate UFFD_WP markers outside uffd-wp VMAs

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UFFD PTE bit handling is a bit like swiss cheese, in particular with
recently added RWP mode. Having uffd-wp markers outside uffd-wp VMAs
already confused this code in the past and resulted in uffd-pte bits
confusing other code later.

Let's play safe and just ignore these markers in hugetlb_no_page(), not
silently propagating the uffd-wp PTE bit.

Link: https://lore.kernel.org/20261015-urgent_fixes-v1-8-42796911043b@kernel.org
Fixes: 2d427bb016 ("mm/userfaultfd: add RWP fault delivery and expose UFFDIO_REGISTER_MODE_RWP")
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Rik van Riel <riel@surriel.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: <stable@vger.kernel.org>
This commit is contained in:
David Hildenbrand (Arm) 2026-10-15 18:07:14 +02:00 committed by Andrew Morton
parent 811777d820
commit c37e9d9411
1 changed files with 4 additions and 1 deletions
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5
mm/hugetlb.c
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@ -5981,8 +5981,11 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
/*
* If this pte was previously wr-protected, keep it wr-protected even
* if populated.
*
* TODO: fix all cases where uffd-wp markers remain in VMAs that are no
* longer registered with uffd.
*/
if (unlikely(pte_is_uffd_wp_marker(vmf->orig_pte)))
if (unlikely(userfaultfd_wp(vma) && pte_is_uffd_wp_marker(vmf->orig_pte)))
new_pte = huge_pte_mkuffd(new_pte);
set_huge_pte_at(mm, vmf->address, vmf->pte, new_pte, huge_page_size(h));