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 73315495025 for ; Tue, 13 Oct 2026 18:32:33 +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=1791916355; cv=none; b=cEipIdxuW1WYpmD8ieKsE+AGgrNMQHE+r4SJDis7XgHzDEkUCxEnmaA0yGH9rDZvfzoZGjLJ5KYFukvVFmQdeCFZ/Q2Jb+kbqE7KXe47775NW8reK1ARBbe04d4gHLDl25e8XKJWrI4on/gT74qEb0bzMn8KxCGBIpH85fPoREk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791916355; c=relaxed/simple; bh=FnkrY+MRt3J2Ogik6L8gFnk4hATMuFao8gO0wrh9rk4=; h=Date:To:From:Subject:Message-Id; b=Fd/suqemOl8DHNBH0AbC0GyYUKWql/u+3eqJABddNgJZxBB+44e78Ve4B1BzxKsyyCYIqiXQpnZViZKw93XwGeKgcZ/iP8W2gKyT3LOI+9Pu3Z7GauHfTNaQErxB5AE8BDnoGJYf7zNzhaYFynamU26mbA9fgEAcU8DOgRPQX68= 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=CMmGlJzd; 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="CMmGlJzd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49B361F00893; Tue, 13 Oct 2026 18:32:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1791916353; bh=2d8IFw+XxZZvijMJrUbia3Aesill+cZAzKQ7anQTcHc=; h=Date:To:From:Subject; b=CMmGlJzdj6F5jDbLzVI+jNlI9ThU/ciIb+qwiCRbv+xcY6iaxoblKtEFgAofAaiqq SjpVbBE02y1Gc5cBOzcK6eO8PykagMy+1wpDLioXZ93zY+R4VJz9edp5asTMCbhFQ1 WHWENu5Go80PRdbCHO/z8aGUdwZ0kv/z0a5CJ0Bk= Date: Tue, 13 Oct 2026 11:32:32 -0700 To: mm-commits@vger.kernel.org,ljs@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-vma-only-allow-mmap-to-clear-vma_maywrite_bit-if-not-mm-managed.patch removed from -mm tree Message-Id: <20261013183233.49B361F00893@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/vma: only allow mmap to clear VMA_MAYWRITE_BIT if not mm-managed has been removed from the -mm tree. Its filename was mm-vma-only-allow-mmap-to-clear-vma_maywrite_bit-if-not-mm-managed.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: "Lorenzo Stoakes (ARM)" Subject: mm/vma: only allow mmap to clear VMA_MAYWRITE_BIT if not mm-managed Date: Fri, 09 Oct 2026 19:04:09 +0100 For ordinary files the only way the VMA_MAYWRITE_BIT flag is cleared is if the underlying file is itself read-only. This means that mprotect() cannot mark a shared mapping of a read-only file as read/write, as doing so would violate the read only attribute, and permit writes. In general, we do not want file systems to be able to do this for read/write files. Doing so would violate fundamental user expectation of file attributes and likely break userspace. However, drivers pose a tricky problem here - the /dev/xxx file may be read/write but provide access to a resource which is fundamentally read-only. Therefore we must allow drivers to be able to clear VMA_MAYWRITE_BIT. To achieve both of these things, forbid this for mm-managed mappings as identified by vma_flags_is_mm_managed(). This constrains this ability to drivers which own the mapping's contents, whether memory-mapped I/O, kernel-allocated pages, or ordinary pages they map themselves, and so define its semantics. Every in-tree mmap hook which clears VMA_MAYWRITE_BIT, some twenty sites across drivers, filesystems and bpf, establishes a mapping which is not mm-managed, with usbmon and the ALSA PCM status page converted earlier in this series to do so. Note that drivers may, if they do not gate on VMA_SHARED_BIT, be able to disable MAP_PRIVATE-file-backed mapping CoW semantics. This is perhaps not always intended, but we retain this capacity to maintain existing behaviour. As no driver which clears VMA_MAYWRITE_BIT establishes an mm-managed mapping, no functional change is intended. Link: https://lore.kernel.org/20261009-b4-mmap-prepare-vma-flag-sanify-v5-15-923b70125b1e@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Andrew Morton Acked-by: Zi Yan Acked-by: David Hildenbrand (Arm) Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Pedro Falcato Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Jonathan Corbet Cc: Greg Kroah-Hartman Cc: Dennis Dalessandro Cc: Jason Gunthorpe Cc: Leon Romanovsky Cc: Paul Moore Cc: Stephen Smalley Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Andrii Nakryiko Cc: Eduard Zingerman Cc: Kumar Kartikeya Dwivedi Cc: Baolin Wang Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lance Yang Cc: Usama Arif Cc: Kiryl Shutsemau Cc: Doug Gilbert Cc: James Bottomley Cc: Martin K. Petersen Cc: Simona Vetter Cc: Helge Deller Cc: Sebastian Reichel Cc: John Hubbard Cc: Peter Xu Cc: Masami Hiramatsu Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: Arnaldo Carvalho de Melo Cc: Namhyung Kim Cc: Mark Rutland Cc: Rik van Riel Cc: Harry Yoo Cc: Juri Lelli Cc: Vincent Guittot Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: David Airlie Cc: Will Deacon Cc: Aneesh Kumar K.V Cc: Nicholas Piggin Cc: Arnd Bergmann Cc: Muchun Song Cc: Oscar Salvador Cc: Matthew Wilcox (Oracle) Cc: Jan Kara Cc: Marc Zyngier Cc: Oliver Upton Cc: Catalin Marinas Cc: Madhavan Srinivasan Cc: Anup Patel Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: Christian Borntraeger Cc: Janosch Frank Cc: Claudio Imbrenda Cc: Alexander Gordeev Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Vasily Gorbik Cc: David S. Miller Cc: Andreas Larsson Cc: Al Viro Cc: Christian Brauner Cc: Matthew Brost Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Chris Li Cc: Kairui Song Cc: Kemeng Shi Cc: Nhat Pham Cc: Baoquan He Cc: Youngjun Park Cc: Johannes Weiner Cc: Qi Zheng Cc: Shakeel Butt Cc: Axel Rasmussen Cc: Yuanchu Xie Cc: Wei Xu Cc: Chengming Zhou Cc: Michal Hocko Cc: Miklos Szeredi Cc: Xu Xin Cc: Ihor Solodrai Cc: Bert Karwatzki --- mm/vma.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/mm/vma.c~mm-vma-only-allow-mmap-to-clear-vma_maywrite_bit-if-not-mm-managed +++ a/mm/vma.c @@ -2816,6 +2816,11 @@ static int mmap_validate(unsigned long o if (WARN_ON_ONCE(!was_maywrite && is_maywrite)) return -EINVAL; + /* mm-managed mappings may not clear VMA_MAYWRITE_BIT. */ + if (vma_flags_is_mm_managed(curr_flags) && + WARN_ON_ONCE(was_maywrite && !is_maywrite)) + return -EINVAL; + return mmap_validate_vma_flags(curr_flags); } _ Patches currently in -mm which might be from ljs@kernel.org are mm-vma-add-and-use-vma__is_fixed_mapping.patch scsi-sg-convert-mmap-hook-to-mmap_prepare-and-rework.patch fbdev-defio-assert-fbinfo_virtfb-drop-vm_io-add-vm_mixedmap.patch hsi-cmt_speech-convert-mmap-hook-to-mmap_prepare-refactor.patch mm-gup-error-out-early-on-vma_mayread_bit-vmas.patch uprobes-remove-vm_io-set-vm_mixedmap-for-mapped-kernel-pages.patch mm-mlock-clear-vma_locked_mask-over-mmap-callback.patch mm-mlock-eliminate-weird-vma_io_bit-abuse-and-simplify.patch mm-vma-enforce-that-mm-managed-mappings-may-not-set-vma_io_bit.patch mm-remove-vma_io_bit-check-in-vma_is_mm_managed.patch mm-remove-hugetlb_inlineh.patch mm-rename-is_vm_hugetlb_page-to-vma_is_hugetlb.patch mm-drop-some-redundant-checks-around-hugetlb-vmas.patch mm-madvise-update-is_valid_guard_vma-to-use-vma_can_merge.patch mm-vma-introduce-vma_is_mm_backed.patch mm-uffd-use-predicates-for-userfaultfd-checks.patch mm-madvise-use-predicates-for-madvise-madv_dofork.patch mm-eliminate-vma_special_flags-usage-when-hugetlb-explicitly-tested.patch mm-eliminate-vma_special_flags-check-in-lru_gen_look_around.patch mm-avoid-use-of-vma_special_flags-in-migrate_vma_setup.patch mm-eliminate-vm_special-vma_special_flags.patch fuse-dax-do-not-set-vm_mixedmap.patch mm-huge_memory-remove-vma_is_special_huge.patch mm-vma-const-ify-vma_assert_stabilised-and-associated-functions.patch mm-implement-and-use-vma_has_anon_rmap-silence-kcsan.patch mm-update-comments-to-refer-to-anon-rmap-rather-than-anon_vma.patch mm-vma-dont-remove-vma-from-rmap-if-pgoff-unchanged.patch