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 ECAF23AD512 for ; Thu, 16 Jul 2026 23:32:56 +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=1784244778; cv=none; b=TKMX96iIU4SwOV0Ea1CzM+KXzVlBhUdqYvdsl3jjg/kwrF8Xodgp6AjRo8ily+BEftDI6mwcGXWzk9uhA1fz6VSdsrWB/AOyOiWmZZhsaDfSpnjL6szFEDWVVowrC1jEC4nW3RRwMZCoMoqkjbO5sSTjvND3+q33DEnBoh7zwIk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784244778; c=relaxed/simple; bh=/5GtYfKLAgZNigWxXX33hROAYBTWcQ7PCvYKRQOISbg=; h=Date:To:From:Subject:Message-Id; b=N1nGubFA+ZCbJ8/aZjt98qz/yZEE7IEPw4JWjkC8eFqMm61rqwYLB+4vFrXVIgJoU2elp+3r9JIgnH7Ujd/sEgKIg9VbyME4AnSQlKcA7smIqxDq8H+EV2I3V+/Rn3i5HVHyryuy34DHBevEjsu9iOI7qTwWfa0eMvrGbdj5bIw= 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=yBqyv90o; 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="yBqyv90o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8D7EF1F000E9; Thu, 16 Jul 2026 23:32:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1784244776; bh=1RwSlRvEwfLkH8kHuMFN1OChamO9jPgjZ6ChS9tygc8=; h=Date:To:From:Subject; b=yBqyv90owcAJJqFrXDpzpmpOY2ebtryJ1SIKVZyOIom0ZhG5G1AmU6LFjHx1e+2MX jC+P7Jia+fV4mf+PpeeRNU5kYemQYox4LoEL3FwRXCs0BAwFIq0mECcxzwxo4o01X+ kpz1f3q64izmHuHIoPQkmjx6KW5cwQgHkZRFCr1s= Date: Thu, 16 Jul 2026 16:32:56 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] x86-mm-pat-acquire-mmap-lock-on-page-table-free-to-avoid-ptdump-uaf.patch removed from -mm tree Message-Id: <20260716233256.8D7EF1F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: x86/mm/pat: acquire mmap lock on page table free to avoid ptdump UAF has been removed from the -mm tree. Its filename was x86-mm-pat-acquire-mmap-lock-on-page-table-free-to-avoid-ptdump-uaf.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Lorenzo Stoakes Subject: x86/mm/pat: acquire mmap lock on page table free to avoid ptdump UAF Date: Tue, 14 Jul 2026 18:24:24 +0100 x86 implements page attribute modification using its Change Page Attributes (CPA) mechanism. This tracks properties of ranges such as cache mode through x86 page attributes, and as part of that logic manipulates kernel page tables. Since commit 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") ranges of kernel page table entries can be collapsed into huge page table entries as part of this logic. As part of this collapse, it frees the page tables which the collapsed entries previously pointed to, and it does so without any relevant locks being held to preclude concurrent kernel page table walkers. The only way this code can be reached is if CPA_COLLAPSE is specified, and this is only set in set_memory_rox() via: set_memory_rox() -> change_page_attr_set_clr() -> cpa_flush() -> cpa_collapse_large_pages() Notable users of this are execmem and bpf when manipulating executable mappings. However, this is problematic for ptdump as it walks ranges it does not own and thus runs the risk of a use-after-free on page tables freed underneath it. Resolve the issue by acquiring the mmap read lock on init_mm which prevents a concurrent ptdump as it acquires the write lock. It is safe to acquire a sleeping lock as all the callers invoke set_memory_rox() from process context and in any case, change_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a mutex, disallowing atomic context here. Link: https://lore.kernel.org/20260714-series-vmap-race-fix-v3-2-b812eccfa0f9@kernel.org Fixes: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") Signed-off-by: Lorenzo Stoakes Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: Dave Hansen 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: Signed-off-by: Andrew Morton --- arch/x86/mm/pat/set_memory.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) --- a/arch/x86/mm/pat/set_memory.c~x86-mm-pat-acquire-mmap-lock-on-page-table-free-to-avoid-ptdump-uaf +++ a/arch/x86/mm/pat/set_memory.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -436,9 +437,16 @@ static void cpa_collapse_large_pages(str flush_tlb_all(); - list_for_each_entry_safe(ptdesc, tmp, &pgtables, pt_list) { - list_del(&ptdesc->pt_list); - pagetable_free(ptdesc); + /* + * ptdump might read these page tables, so avoid a use-after-free by + * acquiring the mmap read lock on init_mm (ptdump acquires the mmap + * write lock). + */ + scoped_guard(mmap_read_lock, &init_mm) { + list_for_each_entry_safe(ptdesc, tmp, &pgtables, pt_list) { + list_del(&ptdesc->pt_list); + pagetable_free(ptdesc); + } } } _ Patches currently in -mm which might be from ljs@kernel.org are 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