linux-kernel - [PATCH v2 2/6] mm/hugetlb: Fix uffd-wp bit lost when unsharing happens

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230417195317.898696-3-peterx@redhat.com>
Date:   Mon, 17 Apr 2023 15:53:13 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mika Penttilä <mpenttil@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>, peterx@...hat.com,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        David Hildenbrand <david@...hat.com>,
        linux-stable <stable@...r.kernel.org>
Subject: [PATCH v2 2/6] mm/hugetlb: Fix uffd-wp bit lost when unsharing happens

When we try to unshare a pinned page for a private hugetlb, uffd-wp bit can
get lost during unsharing.  Fix it by carrying it over.

This should be very rare, only if an unsharing happened on a private
hugetlb page with uffd-wp protected (e.g. in a child which shares the same
page with parent with UFFD_FEATURE_EVENT_FORK enabled).

Cc: linux-stable <stable@...r.kernel.org>
Fixes: 166f3ecc0daf ("mm/hugetlb: hook page faults for uffd write protection")
Reported-by: Mike Kravetz <mike.kravetz@...cle.com>
Reviewed-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 mm/hugetlb.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0213efaf31be..cd3a9d8f4b70 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5637,13 +5637,16 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
 	spin_lock(ptl);
 	ptep = hugetlb_walk(vma, haddr, huge_page_size(h));
 	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
+		pte_t newpte = make_huge_pte(vma, &new_folio->page, !unshare);
+
 		/* Break COW or unshare */
 		huge_ptep_clear_flush(vma, haddr, ptep);
 		mmu_notifier_invalidate_range(mm, range.start, range.end);
 		page_remove_rmap(old_page, vma, true);
 		hugepage_add_new_anon_rmap(new_folio, vma, haddr);
-		set_huge_pte_at(mm, haddr, ptep,
-				make_huge_pte(vma, &new_folio->page, !unshare));
+		if (huge_pte_uffd_wp(pte))
+			newpte = huge_pte_mkuffd_wp(newpte);
+		set_huge_pte_at(mm, haddr, ptep, newpte);
 		folio_set_hugetlb_migratable(new_folio);
 		/* Make the old page be freed below */
 		new_folio = page_folio(old_page);
-- 
2.39.1