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 AC6AE42DFEA for ; Mon, 20 Jul 2026 14:29:44 +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=1784557785; cv=none; b=u+uG4om+ZTDE5qqWenk1hKinmYW3LgDe9W8J/qO9As8qli3xWPODQB+BiM3v7wYXfB5Aq4cr5+7ZzB/sNzMk1u8ZrdnpkLAjJUdvDJC8ER1Py0Pn/0z05BHZfq8XhVChjISUoHRZ7J6OAotZEXOkZTePgvjox4ThoY5wEpXgUrU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784557785; c=relaxed/simple; bh=VaKH0YZxWN/abgng93Eq1J4cySP4/qEMgiVuuYHik4c=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=XRkGTg6vxdlzniNLTU4949Jk4W8rdvOd/mJXu2PRwzgYoVsRrm7DmQ5Cl8uXowo79YzL3A0LECkOy2DWs+ctmA6Ovt9LFl8lSWnOXkc1G8baBYOCiMzFOag041TpJUrofjwywSLg0opcvYVPgwWcZL6GfP1m+i6HCCYJIdn2A2A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SKLGANPd; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="SKLGANPd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D73A1F000E9; Mon, 20 Jul 2026 14:29:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784557784; bh=XAJjm66ji3gGXCvIC06UGiv/QjJ7Ijg8auZADKhzBN0=; h=Subject:To:Cc:From:Date; b=SKLGANPdzk5vHOhetHzZdWLW0twoIRQlr2PlvxUpxZk01OYClnDyh/CYGu8xDgcMf j0kvbJnioDVyMsW8CtacymUqlUuy0HbkOUQhBvy+l0bLOI1s2QW70fVN8NV/wfwIJ7 CXFNQXqkRMvrNWtLNavBLJF14Vrg7MA/jX3nmkcQ= Subject: FAILED: patch "[PATCH] fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update" failed to apply to 6.18-stable tree To: kas@kernel.org,akpm@linux-foundation.org,balbirs@nvidia.com,david@kernel.org,dev.jain@arm.com,ljs@kernel.org,mhocko@suse.com,peterx@redhat.com,rppt@kernel.org,sashiko-bot@kernel.org,stable@vger.kernel.org,surenb@google.com,vbabka@kernel.org Cc: From: Date: Mon, 20 Jul 2026 16:29:35 +0200 Message-ID: <2026072035-discolor-busily-8d3a@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 04718f7c9290f95385f0dd328758753dc1c36dec # git commit -s git send-email --to '' --in-reply-to '2026072035-discolor-busily-8d3a@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 04718f7c9290f95385f0dd328758753dc1c36dec Mon Sep 17 00:00:00 2001 From: "Kiryl Shutsemau (Meta)" Date: Fri, 29 May 2026 18:23:25 +0100 Subject: [PATCH] fs/proc/task_mmu: fix make_uffd_wp_huge_pte() prot-update race 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 diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 1e3a15bf46f4..e21a38ac745b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2610,12 +2610,16 @@ static void make_uffd_wp_huge_pte(struct vm_area_struct *vma, 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 */