From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 228C72F6188; Tue, 9 Jun 2026 01:22:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780968156; cv=none; b=e0H4CiOc4nC6loGlLRAYwaKO+qmIBSUKx/YO/Y3fPtQHmlj6kMS5/VKFg1Xlm1Jto5HtCsKdAw9ZzmL/kfKDpGKnb6p015fau5AjVsL+oJleHuCfkcnGTXwNmAu9s3CsTFz8//MUKOHMFRtQPRFBmT0lqn5XECYBBhwly2fIWuQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780968156; c=relaxed/simple; bh=BxkIzcFktqZXGj1ro6gCyhWt5mGd3CyEZcAw8xGeD0M=; h=Date:To:From:Subject:Message-Id; b=UrAKOuXp7S1YwNUIw6mVqHGJuSco+Q6Nbfc1+Bgh25onYu+bxKo/0E961fQZN7WYkm8fMzxlmt9rhqy0t0mv2yJVyTkI4trYT5F21SXFzALwvKPJpCLQPUeOwI5LmqZ/b+y6zAH05MXWOGEJmmgtHwKXjnY41Ul6zAUojrziFNs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=ziQMSZ5W; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="ziQMSZ5W" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E94F31F00893; Tue, 9 Jun 2026 01:22:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1780968155; bh=MMfwCnAREdwb+cnYQp+Ya9WougO8T3seWaQhwmlD+O4=; h=Date:To:From:Subject; b=ziQMSZ5W5COmmDjzcIY8ihEPJS4TSwzKQRHREEvT171hVFUzfQGenfvpwLSveLARV cOzMuXlU1mPaDU6fjQ6l2xsq9bcJPNoyhv5aIETt8Qy0i+LPKIj5ciuNfsQ1AFN+67 tOKHZq7qxH1Spj0KRJLpZY9VDr/7xDS6VGfcotCs= Date: Mon, 08 Jun 2026 18:22:34 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,surenb@google.com,stable@vger.kernel.org,sashiko-bot@kernel.org,rppt@kernel.org,peterx@redhat.com,mhocko@suse.com,ljs@kernel.org,dev.jain@arm.com,david@kernel.org,balbirs@nvidia.com,kas@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] fs-proc-task_mmu-fix-make_uffd_wp_huge_pte-prot-update-race.patch removed from -mm tree Message-Id: <20260609012234.E94F31F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race has been removed from the -mm tree. Its filename was fs-proc-task_mmu-fix-make_uffd_wp_huge_pte-prot-update-race.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: "Kiryl Shutsemau (Meta)" Subject: fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race Date: Fri, 29 May 2026 18:23:25 +0100 Patch series "userfaultfd/pagemap: pre-existing fixes". These are pre-existing bug fixes that were carried at the front of the userfaultfd RWP working-set-tracking series up to v5 [1]. Per review feedback that fixes should not sit in the middle of a feature series, they are split out and sent on their own; the RWP series is reposted rebased on top of this. All six were flagged by the Sashiko AI review of the RWP series and carry Reported-by: Sashiko AI review . They are independent of RWP, apply to mm-new directly, and carry Cc: stable@. 1: fs/proc/task_mmu: a missing huge_ptep_modify_prot_start() in make_uffd_wp_huge_pte() can lose hardware Dirty/Accessed updates when PAGEMAP_SCAN write-protects a hugetlb PTE. 2: fs/proc/task_mmu: pagemap_scan_hugetlb_entry() compares the range against HPAGE_SIZE rather than the hstate page size, so it never write-protects gigantic hugetlb pages. 3: fs/proc/task_mmu: PAGEMAP_SCAN with PM_SCAN_WP_MATCHING over an unpopulated hugetlb range self-deadlocks -- pagemap_scan_pte_hole() calls uffd_wp_range() while walk_hugetlb_range() holds the hugetlb vma lock for read, and hugetlb_change_protection() then takes it for write. Install the marker inline instead. 4: mm/huge_memory: change_non_present_huge_pmd() drops pmd_swp_uffd_wp on a device-private PMD permission downgrade, silently losing the uffd-wp marker. 5: userfaultfd: must_wait() applies pte_write() to a locklessly read PTE without checking pte_present(), so swap/migration entries decode random offset bits and a thread can stay parked on a stale fault. 6: userfaultfd: __VMA_UFFD_FLAGS feeds VMA_UFFD_MINOR_BIT (41) to mk_vma_flags() unconditionally, an out-of-bounds write into the single-word vma_flags_t on 32-bit. Build the mask from config-gated per-mode masks so an unavailable bit is never materialised. This patch (of 6): make_uffd_wp_huge_pte() arms the UFFD_WP bit on a present HugeTLB PTE by calling huge_ptep_modify_prot_commit() with a ptent snapshot that was fetched without the corresponding huge_ptep_modify_prot_start(). The start helper is what atomically clears the entry so the kernel-owned snapshot stays consistent until the commit; without it, the hardware may set Dirty or Accessed in the live PTE between the original read and the commit, and huge_ptep_modify_prot_commit() (whose generic implementation just calls set_huge_pte_at()) then writes the stale snapshot back over the live hardware bits, losing the update. The non-hugetlb sibling make_uffd_wp_pte() does this correctly via ptep_modify_prot_start() / ptep_modify_prot_commit(). Mirror that pattern for the present-PTE branch. The migration case stays as-is -- migration entries are non-present, so there's no hardware update to race against. Link: https://lore.kernel.org/20260529172331.356655-1-kas@kernel.org Link: https://lore.kernel.org/20260529172331.356655-2-kas@kernel.org Link: https://lore.kernel.org/all/20260526130509.2748441-1-kirill@shutemov.name/ [1] Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") Signed-off-by: Kiryl Shutsemau Reported-by: Sashiko AI review Reviewed-by: Lorenzo Stoakes Reviewed-by: Dev Jain Cc: David Hildenbrand Cc: Michal Hocko Cc: Mike Rapoport Cc: Peter Xu Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Balbir Singh Cc: Signed-off-by: Andrew Morton --- fs/proc/task_mmu.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- a/fs/proc/task_mmu.c~fs-proc-task_mmu-fix-make_uffd_wp_huge_pte-prot-update-race +++ a/fs/proc/task_mmu.c @@ -2610,12 +2610,16 @@ static void make_uffd_wp_huge_pte(struct if (softleaf_is_hwpoison(entry) || softleaf_is_marker(entry)) return; - if (softleaf_is_migration(entry)) + if (softleaf_is_migration(entry)) { set_huge_pte_at(vma->vm_mm, addr, ptep, pte_swp_mkuffd_wp(ptent), psize); - else - huge_ptep_modify_prot_commit(vma, addr, ptep, ptent, - huge_pte_mkuffd_wp(ptent)); + } else { + pte_t old_pte, new_pte; + + old_pte = huge_ptep_modify_prot_start(vma, addr, ptep); + new_pte = huge_pte_mkuffd_wp(old_pte); + huge_ptep_modify_prot_commit(vma, addr, ptep, old_pte, new_pte); + } } #endif /* CONFIG_HUGETLB_PAGE */ _ Patches currently in -mm which might be from kas@kernel.org are