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 3FB22373BF1; Tue, 14 Jul 2026 01:58:21 +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=1783994302; cv=none; b=UgMPlhFKIhf1mamu+hLkBAEg3vyj3//Ff2c45W+a8CshaHr1xLg9UywolVv1mGtuHCRf+QSbkh6+MeU+63N+v0DUNKrNEtnfJl5wZwNaiqhnC55lrGu63vMCpaJ/EqfV5q9fVi3SzIxa+MU8n2Y71XAB1bfX3VmFeL+rUfe/AFc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783994302; c=relaxed/simple; bh=fl31rGcFT6HujSlV/fQT7vDTD321rMfIdAt4VOCGx1I=; h=Date:To:From:Subject:Message-Id; b=sPX0zESm/jSrMjXBQroZKmu6v31JxK1KJt8Ipsb5qsRGsl1OEpNSyb7jXZa04obXsDyvnSgtebhbAfcQjbpIkQcUHlbUGvo49dRTcRfbi0BtPxlNnSc7JUEqtOi7lSVQfVqiHqeVUvaXsTX73xnHw32/Jc36xkl9ageF43j1w1I= 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=FB2QarWl; 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="FB2QarWl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7A8F1F000E9; Tue, 14 Jul 2026 01:58:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1783994300; bh=XRheWPJr1U71aOEEyyupXulvMMTsavsCOIl5GOuZtWw=; h=Date:To:From:Subject; b=FB2QarWl3+AWM8uwu/NSoNhZ+pf3gFMIqQRj7M8nNDm6Of9aWEfx9ICJxvAI5hnsJ KsRyx0A5K0W7B27QLFRFJQyL7PRpHoiF2UfIhT0Hv3xWyEY4FlOnuzKMKcvLI6+iiS 8X0kP5PwP7xI9mWnsm78fD1lBl0c/wpq94ON10XA= Date: Mon, 13 Jul 2026 18:58:20 -0700 To: mm-commits@vger.kernel.org,will@kernel.org,vbabka@kernel.org,urezki@gmail.com,toshi.kani@hpe.com,surenb@google.com,stable@vger.kernel.org,shakeel.butt@linux.dev,ryan.roberts@arm.com,rppt@kernel.org,peterz@infradead.org,mingo@redhat.com,mhocko@suse.com,luto@kernel.org,liam@infradead.org,kas@kernel.org,hpa@zytor.com,dev.jain@arm.com,david@kernel.org,catalin.marinas@arm.com,bp@alien8.de,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch added to mm-hotfixes-unstable branch Message-Id: <20260714015820.D7A8F1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/ptdump: always stabilise against page table freeing using init_mm has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ptdump-always-stabilise-against-page-table-freeing-using-init_mm.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 Subject: mm/ptdump: always stabilise against page table freeing using init_mm Date: Sun, 12 Jul 2026 11:42:26 +0100 x86 and arm64 invoke ptdump_walk_pgd() with non-init_mm mm whilst still walking kernel page table ranges. For x86 this is done in ptdump_curknl_show() and ptdump_efi_show(), the first passing current->mm, and the second passing efi_mm (we reach kernel mappings that init_mm protects for current->mm due to x86 cloning shared kernel page tables for arbitrary mm's). arm64 does so via ptdump_debugfs_register(), configured by efi_ptdump_info for efi ranges against efi_mm. The init_mm mmap lock is used to stabilise page table freeing against ptdump, so take a nested lock on init_mm to ensure that we are correctly stabilised. We take this after mmap write locking the non-init_mm mm. Nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. The preceding patches in this series updated the two cases which can cause races with ptdump in init_mm ranges - vmap and x86 CPA huge page promotion. For arm64, commit fa93b45fd397 ("arm64: Enable vmalloc-huge with ptdump") already provides exclusion against init_mm for the vmap case, which this patch also pairs with. 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. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code. We do not need to check for walk.mm being non-NULL, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The rest of this code is exactly as it would be if invoking walk_kernel_page_table_range(), only now it's far clearer that that's the case. Link: https://lore.kernel.org/20260712-series-vmap-race-fix-v2-3-ad134cc3a12a@kernel.org Fixes: b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table") Signed-off-by: Lorenzo Stoakes Reviewed-by: Mike Rapoport (Microsoft) Cc: Andy Lutomirski Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: David Hildenbrand Cc: Dev Jain Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Kiryl Shutsemau 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: 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 mm-vmalloc-acquire-init_mm-lock-on-huge-vmap-to-avoid-ptdump-uaf.patch x86-mm-pat-acquire-mmap-lock-on-page-table-free-to-avoid-ptdump-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