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 2917B373BF1; Tue, 14 Jul 2026 01:58:18 +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=1783994300; cv=none; b=fWDcwHbfkQeHoYgyNTCkluULkhOT2eEgh+0CpxtMWuucljyXdYPbVIRlVCgQEYLRJhnv4lwGd1QGDpmBjLvNGTWA8AJJtQPUpExtqUkxPfDmWfGJwZfwvG0lVxUAc04ES3StYXt4zNXyBMhHxg2QdsMKOSjHoW+Xcdgmd9cdTYk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783994300; c=relaxed/simple; bh=y01tXma0wW2BpgelOexdJtkRDXuiUI+bQs9NwB75r/M=; h=Date:To:From:Subject:Message-Id; b=uaqVPxIKRKFoKHG7Gdl0VXqDRttVtB69QvQmkNXeX8VCTP8HN8DLruRfMzARLXzGixxibEoJL32Buo12SfDwA0HVnTIQgbHcytvtrF1xYBlSPUMLWcytxlzG0JGXC6cnOsNNLDmM0PyAgHeDhwHhF0mDn/mTFqAm9tVXzlQR/Uw= 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=FYrPMwZI; 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="FYrPMwZI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 954341F00A3A; Tue, 14 Jul 2026 01:58:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1783994298; bh=c2UIh9tC8VF22BR+MQ283JoXr4ROMHRzw06ys/S0os4=; h=Date:To:From:Subject; b=FYrPMwZIBRaFqdKRtwSfwZAH/XBAk3MDV4StylBgTiudqFv4rId6tzp1iNeCkkLlw uWFim3m6KJxm3Pzn7K8ck6m8B3fUnV9dCX87zltVqd7EyghZnvj6g4qh7aomZMaEdd uRy60z/oKl4FLLmUY/ix/bp0SQG4NZNKf1XZqpvs= Date: Mon, 13 Jul 2026 18:58:18 -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: + x86-mm-pat-acquire-mmap-lock-on-page-table-free-to-avoid-ptdump-uaf.patch added to mm-hotfixes-unstable branch Message-Id: <20260714015818.954341F00A3A@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 mmap lock on page table free to avoid ptdump UAF has been added to the -mm mm-hotfixes-unstable branch. Its filename is x86-mm-pat-acquire-mmap-lock-on-page-table-free-to-avoid-ptdump-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-mmap-lock-on-page-table-free-to-avoid-ptdump-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 Subject: x86/mm/pat: acquire mmap lock on page table free to avoid ptdump UAF Date: Sun, 12 Jul 2026 11:42:25 +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 to provide mutual exclusion against ptdump, which acquires the init_mm 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/20260712-series-vmap-race-fix-v2-2-ad134cc3a12a@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) 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-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