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 B1E1C3AD539 for ; Thu, 16 Jul 2026 23:32:58 +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=1784244780; cv=none; b=lX60ojqJtQvAIBAeZDH8DnTrX4VfNCRr3LRvl8ojiwpSNyND/kDNB8IJHSyt7P/PfmZxY/yXqJpJ0EBrz7XOitcKy0M6GxmXj6rkV++rfXqP5O0TPcg6ATF0eyiAu5r4e3WqBS6XNvBwRJ4R3yQmVhGUvZyllp02aDFlhIP1rPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784244780; c=relaxed/simple; bh=GNxvw4PjywGI8DJ61OybvTPOd9qasDbsfo99GHW+WVI=; h=Date:To:From:Subject:Message-Id; b=KyC/MQa1PFjJ36FxDw3TUbOjjSZ8TicAS0nITdxVBRP/QrcsFI2UNpVNfW0VdZxuOr7LyBEeWo/TXO3Iqm2cR1eyDQB6yAZkN2p2taaUgRh1wcZkIydSDwZkyvfJNGvYYo6kiE5xgkGM3o2Linj73tBO6Ug13my+sErkRlVcg6o= 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=xqz99WVF; 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="xqz99WVF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 544131F00A3A; Thu, 16 Jul 2026 23:32:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1784244778; bh=xVx5yQECk96xAC8VKWn/BxSVCUAOUjjSUczy9E4BPRY=; h=Date:To:From:Subject; b=xqz99WVF6eJYUNr1v4gwxnNToXtWNccUYVhTsGq9/EonQdfkN/plSMNPu/PagUJgV PkmewGHnQdJnrWutLbcQfkXcqUF35HauMreW+d+YV0R3LE8bmmrag+Q/5inR+LDyDf hAzoZ2g0t/P6xj7dTj/Qfww35d/rnms5v333qNjg= Date: Thu, 16 Jul 2026 16:32:57 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch removed from -mm tree Message-Id: <20260716233258.544131F00A3A@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/ptdump: always stabilise against page table freeing using init_mm has been removed from the -mm tree. Its filename was mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Lorenzo Stoakes Subject: mm/ptdump: always stabilise against page table freeing using init_mm Date: Tue, 14 Jul 2026 18:24:25 +0100 Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commit b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table"), so we target this in the Fixes tag. Link: https://lore.kernel.org/20260714-series-vmap-race-fix-v3-3-b812eccfa0f9@kernel.org Fixes: b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table") Signed-off-by: Lorenzo Stoakes Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Kiryl Shutsemau Cc: Andy Lutomirski Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: David Hildenbrand Cc: Dev Jain Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Liam R. Howlett Cc: Michal Hocko 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: Dave Hansen Cc: Signed-off-by: Andrew Morton --- mm/pagewalk.c | 14 +++++++++----- mm/ptdump.c | 7 +++++++ 2 files changed, 16 insertions(+), 5 deletions(-) --- a/mm/pagewalk.c~mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm +++ a/mm/pagewalk.c @@ -702,12 +702,16 @@ int walk_page_range_debug(struct mm_stru * to account for page table freeing on vmap huge page mapping. */ mmap_assert_write_locked(mm); + /* + * x86, arm64 ptdump allow walks of efi mm's and x86 ptdump allows walks + * of arbitrary mm's. + * + * However, they both must also hold the init_mm lock to account for + * concurrent kernel page table freeing. + */ + mmap_assert_write_locked(&init_mm); - /* For convenience, we allow traversal of kernel mappings. */ - if (mm == &init_mm) - return walk_kernel_page_table_range(start, end, ops, - pgd, private); - if (start >= end || !walk.mm) + if (start >= end) return -EINVAL; if (!check_ops_safe(ops)) return -EINVAL; --- a/mm/ptdump.c~mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm +++ a/mm/ptdump.c @@ -178,11 +178,18 @@ void ptdump_walk_pgd(struct ptdump_state get_online_mems(); mmap_write_lock(mm); + /* To stabilise kernel page tables we must hold the init_mm lock too. */ + if (mm != &init_mm) + mmap_write_lock_nested(&init_mm, SINGLE_DEPTH_NESTING); + while (range->start != range->end) { walk_page_range_debug(mm, range->start, range->end, &ptdump_ops, pgd, st); range++; } + + if (mm != &init_mm) + mmap_write_unlock(&init_mm); mmap_write_unlock(mm); put_online_mems(); _ Patches currently in -mm which might be from ljs@kernel.org are 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