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 19B4B3264F1 for ; Fri, 17 Jul 2026 19:29:31 +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=1784316573; cv=none; b=Fs1YiyR/gInXBtw6fpBjzIZsdx+t2LOa3cSKWEHbtHtvFVc5DkNVYrV1u14dJklcYJHNgpgvvFrqoA8w1CYtMJwvy1s3cJ0oy2LIAiJ1U5av+4kJb/4vM7zqnaN91K7YO5dC6SbwORSnqK/TM2YncLpVauSrKpuu9pgo+elIjTA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784316573; c=relaxed/simple; bh=9QnN9tWQx+JSNwmgJPIUm10U19cR7qThCEjWPwUAlnA=; h=Date:To:From:Subject:Message-Id; b=QekV56MiUaYXiXS0ByPxe2CjwYGgB1J0P3gnEE0+MztRlQ6lXYSvM86EsuKs74VCA3lQxKHThZfhMD2ICnSTc92eDfVB9X96XvvuJs8J9w7TrSVmFdqlquSv6s6OQ9TyCqX/GJm2MGxM7ODYM9hBiWTtmLlvQKiMfB5MCCjrcNw= 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=MsUPyl+S; 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="MsUPyl+S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1E671F000E9; Fri, 17 Jul 2026 19:29:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1784316571; bh=c0zJ0r2f2aYa6cmoAxoGaEn3RxqeaI3FqMFpEVADIxY=; h=Date:To:From:Subject; b=MsUPyl+SzLQQoySl0ZyXGLOTi+X5Y5xHLp9e38pMzJA+BaQjw2y9mPvhKaQuSy96W lrz/ciAOMrNmjei8FMGsZ0vN8yzKQhyBSoQ75oHMLXOi/HHT0ac46z/jEQSfXmU5oM f7qwkr3t6iwjlR77q9nxGae7HR2HqPP9LtYVwL5s= Date: Fri, 17 Jul 2026 12:29:31 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf.patch added to mm-hotfixes-unstable branch Message-Id: <20260717192931.B1E671F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: x86/mm/pat: acquire init_mm read lock on attribute change to avoid UAF has been added to the -mm mm-hotfixes-unstable branch. Its filename is x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: "Lorenzo Stoakes (ARM)" Subject: x86/mm/pat: acquire init_mm read lock on attribute change to avoid UAF Date: Fri, 17 Jul 2026 18:30:09 +0100 A previous commit protected us against races between ptdump and CPA collapse, however one still exists between attribute changes and collapse as reported by Denis V. Lunev (linked). When an attribute change arises, a lockless page table walker obtains a PTE entry, which is later written to via set_pte_atomic(): ... -> change_page_attr_set_clr() -> __change_page_attr_set_clr() -> __change_page_attr() -> _lookup_address_cpa() -> lookup_address_in_pgd_attr() -> [ lockless page table walker ] -> set_pte_atomic() There is nothing preventing a concurrent CPA collapse which can free the PTE that was retrieved here, resulting in a use-after-free. With the mmap write lock taken on init_mm over CPA collapse, we can now resolve this race by acquiring an mmap read lock on init_mm over __change_page_attr_set_clr(). This locks across the whole operation over which the walk and the PTE entry write occurs, solving the race. It is safe to do this here, as no spinlocks are held upon entry to __change_page_attr_set_clr(). The CPA_COLLAPSE flag is only set by set_memory_rox(), which exclusively operates upon vmalloc ranges, and on x86 only within the module mapping space. This is important, because some callers directly invoke __change_page_attr_set_clr(), bypassing this lock. However, none of these operate within the module mapping space. * cpa_process_alias() - a recursive helper called by __change_page_attr_set_clr(). * __set_memory_enc_pgtable() - operates on the direct mapping and (via __vmbus_establish_gpadl()) the vmalloc mapping space. * __set_pages_[n]p() - called by set_direct_map_[invalid, default, valid]_noflush(), __kernel_map_pages() - operates on the direct map. * kernel_[un]map_pages_in_pgd() - operates on EFI ranges. This work is based upon Denis V. Lunev's excellent analysis of the bug with gratitude. Link: https://lore.kernel.org/all/20260626163213.2284080-1-den@openvz.org/ Link: https://lore.kernel.org/20260717-series-vmap-race-fix-v5-3-606a0ac6d3e5@kernel.org Fixes: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") Signed-off-by: Lorenzo Stoakes (ARM) Cc: Andy Lutomirski Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Dave Hansen Cc: David Carlier Cc: David Hildenbrand (Arm) Cc: Dev Jain Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Kiryl Shutsemau Cc: Liam R. Howlett Cc: Michal Hocko Cc: Mike Rapoport (Microsoft) Cc: Peter Zijlstra Cc: Ryan Roberts Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Toshi Kani Cc: "Uladzislau Rezki (Sony)" Cc: Vlastimil Babka Cc: Will Deacon Cc: Signed-off-by: Andrew Morton --- arch/x86/mm/pat/set_memory.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/arch/x86/mm/pat/set_memory.c~x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf +++ a/arch/x86/mm/pat/set_memory.c @@ -2122,7 +2122,9 @@ static int change_page_attr_set_clr(unsi cpa.curpage = 0; cpa.force_split = force_split; - ret = __change_page_attr_set_clr(&cpa, 1); + /* Avoid race with concurrent CPA collapse. */ + scoped_guard(mmap_read_lock, &init_mm) + ret = __change_page_attr_set_clr(&cpa, 1); /* * Check whether we really changed something: _ Patches currently in -mm which might be from ljs@kernel.org are mm-vmalloc-acquire-init_mm-lock-on-huge-vmap-to-avoid-ptdump-uaf.patch x86-mm-pat-acquire-init_mm-write-lock-on-collapse-to-avoid-uaf.patch x86-mm-pat-acquire-init_mm-read-lock-on-attribute-change-to-avoid-uaf.patch mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch arm64-remove-redundant-concurrent-ptdump-uaf-mitigation.patch mm-move-alloc-tag-to-mm.patch mm-move-vma_start_pgoff-into-mmh-and-clean-up.patch mm-add-kdoc-comments-for-vma_start-last_pgoff.patch tools-testing-vma-use-vma_start_pgoff-in-merge-tests.patch mm-introduce-and-use-vma_end_pgoff.patch mm-rmap-update-mm-interval_treec-comments.patch mm-rmap-parameterise-vma_interval_tree_-by-address_space.patch mm-rmap-elide-unnecessary-static-inlines-in-interval_treec.patch mm-rmap-rename-vma_interval_tree_-to-mapping_rmap_tree_.patch mm-rmap-parameterise-anon_vma_interval_tree_-by-anon_vma.patch mm-rmap-rename-anon_vma_interval_tree_-params-and-use-pgoff_t.patch mm-rmap-rename-anon_vma_interval_tree_-to-anon_rmap_tree_.patch maintainers-move-mm-interval_treec-to-rmap-section.patch mm-vma-introduce-and-use-vmg_pages-vmg__pgoff.patch mm-vma-clean-up-anon_vma_compatible.patch mm-vma-refactor-vmg_adjust_set_range-for-clarity.patch mm-vma-minor-cleanup-of-expand_.patch mm-introduce-and-use-linear_page_delta.patch mm-vma-use-vma_start_pgoff-linear_page_index-in-mm-code.patch mm-prefer-vma__pgoff-to-vma-vm_pgoff-in-kernel.patch mm-vma-remove-duplicative-vma_pgoff_offset-helper.patch mm-use-linear_page_-consistently.patch mm-vma-introduce-vma_assert_can_modify.patch mm-vma-add-and-use-vma__pgoff.patch mm-vma-move-__install_special_mapping-to-vmac.patch mm-vma-make-vma_set_range-static-drop-insert_vm_struct-decl.patch mm-vma-update-vma_shrink-to-not-pass-start-pgoff-parameters.patch mm-vma-update-vmg_adjust_set_range-to-offset-pgoff-instead.patch mm-vma-slightly-rework-the-anonymous-check-in-__mmap_new_vma.patch mm-vma-introduce-and-use-vma_set_pgoff.patch mm-vma-correct-incorrect-vmah-inclusion.patch mm-vma-use-guard-clauses-in-can_vma_merge_.patch tools-testing-vma-default-vma-mm-flag-bits-to-64-bit.patch tools-testing-vma-output-compared-expression-on-assert_.patch mm-introduce-vma_flags_can_grow-and-vma_can_grow.patch mm-vma-update-do_mmap-to-use-vma_flags_t.patch mm-convert-__get_unmapped_area-to-use-vma_flags_t.patch mm-update-generic_get_unmapped_area-to-use-vma_flags_t.patch mm-prefer-mm-def_vma_flags-in-mm-logic.patch mm-vma-convert-vm_pgprot_modify-to-use-vma_flags_t-and-rename.patch mm-vma-rename-vma_get_page_prot-to-vma_flags_to_page_prot.patch mm-introduce-vma_get_page_prot-and-use-it.patch mm-vma-update-create_init_stack_vma-to-use-vma_flags_t.patch mm-vma-convert-miscellaneous-uses-of-vma-flags-in-core-mm.patch mm-mlock-convert-mlock-code-to-use-vma_flags_t.patch mm-mprotect-convert-mprotect-code-to-use-vma_flags_t.patch mm-mremap-convert-mremap-code-to-use-vma_flags_t.patch mm-mseal-remove-superfluous-comments-fix-confusion-around-mm.patch mm-mseal-limit-scope-of-mseal-address-zero-to-address-zero.patch mm-mseal-remove-further-superfluous-comments-do_mseal.patch