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 1D90747C0E3; Tue, 8 Sep 2026 20:17:13 +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=1788898635; cv=none; b=aQSWWTHeDP3GdYziXfUOCMKh5ypObCTbXRGrkVT5B2xAyHwL7OOMQ4eRy4xSEFFLQsnKt/IiR/wAEhjuaCnDjKn5gxDXR0QHWj6Kp8B0cAzNoSMWu4UEK6b0Rk/OPcocjtDdeIt36DBdzohrNQC7V23HD3kkBvTYHG8+EjsXT08= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788898635; c=relaxed/simple; bh=RaKyg3GqRiVqHvw/UDaaHvGcpLhQwigi+RNlsL2zffs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=majMBsUO1SRmgd3f+m8S0G7MnPsVXxS7tN5RIEGsoGyD5m6Uq67D4lELkZ4CbhVyf2Qrd+VeTIkdehBhYZSVGhF31s8Zyr6oLGIzVvntQc3Y6Wj7OEpDdZ6jASr1OCuKATB8bwkEIag6d/BebtnqOlvXy++Zx4hB5siUIeWvpRI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WCx9g0et; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WCx9g0et" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9BD71F00A3A; Tue, 8 Sep 2026 20:16:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788898633; bh=9WoUWUiccCZ5pmncdG/fVn1uDF622HEjGzqeAT5aHc8=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=WCx9g0etxmzhUw/9vx7dYEuk+1E+t7RRF5GYxZ3UboiiICcZJ2Z9VJXIAX5jvZAuK yLn3n9H2CIkNxPVJIviLI/un0CQOivB5urZe9HHAgD5DOtxto4kGoralvGL6kuQxq7 WlJdP4LsB8jP3OaO+x7IB2Mv8LkIcnHT+PIwoP8WVj8TGNcEmoljLAKM1f26rjlYBg KHgC8wVn6x7kLvbLQC+H30sQyVOp0lZUZU9rB9+gs97wte01EHALW54o2MKn9uudGh FvY0e3bpNwXp7EH2Agf5q2IWP50fU9Z2s03D2k/bOK8gl4G1EEOPz807EajKpcBayM cZJmMvliLRSAQ== From: "Lorenzo Stoakes (ARM)" Date: Tue, 08 Sep 2026 21:01:35 +0100 Subject: [PATCH 31/39] mm/uffd: use predicates for userfaultfd checks Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260908-b4-mmap-prepare-vma-flag-sanify-v1-31-dacf19cce22b@kernel.org> References: <20260908-b4-mmap-prepare-vma-flag-sanify-v1-0-dacf19cce22b@kernel.org> In-Reply-To: <20260908-b4-mmap-prepare-vma-flag-sanify-v1-0-dacf19cce22b@kernel.org> To: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Greg Kroah-Hartman , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Paul Moore , Stephen Smalley , Jaroslav Kysela , Takashi Iwai , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" , Jaya Kumar , Simona Vetter , Helge Deller , Sebastian Reichel , John Hubbard , Peter Xu , Masami Hiramatsu , Oleg Nesterov , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Rik van Riel , Harry Yoo , Juri Lelli , Vincent Guittot , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Arnd Bergmann , Muchun Song , Oscar Salvador , "Matthew Wilcox (Oracle)" , Jan Kara , Marc Zyngier , Oliver Upton , Catalin Marinas , Madhavan Srinivasan , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , "David S. Miller" , Andreas Larsson , Alexander Viro , Christian Brauner , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park , Johannes Weiner , Qi Zheng , Shakeel Butt , Axel Rasmussen , Yuanchu Xie , Wei Xu , Xu Xin , Chengming Zhou , Michal Hocko , Miklos Szeredi Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-usb@vger.kernel.org, linux-rdma@vger.kernel.org, selinux@vger.kernel.org, linux-sound@vger.kernel.org, bpf@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-trace-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, fuse-devel@lists.linux.dev, "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=2289; i=ljs@kernel.org; h=from:subject:message-id; bh=RaKyg3GqRiVqHvw/UDaaHvGcpLhQwigi+RNlsL2zffs=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLIWZG6N47m4kJcv6WDE48sr8nKPqpXlTvmzNeP1N5ct/ 8WWxMz/0VHKwiDGxSArpsjy/Iv4/iCRsHmdF/zdYOawMoEMYeDiFICJrHFkZPivHvnoI//nC3// vu0/ayir/68l9MOiJTsmir23Xe51QtWZkWHVl+PpG7ifX94VlC64cdvh6P9OBZ7sQWuMT79TX6r 6uowdAA== X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Rather than directly checking VMA flags, use the newly introduced vma_is_kernel_owned() and vma_is_persistent() helpers in userfaultfd when assessing VMA suitability for userfaultfd and UFFDIO_MOVE. Update vma_move_compatible() so it's expressed in terms of VMA characteristics rather than arbitrary flags. Additionally, update the use of the deprecated VMA flag API when checking VMA_SHADOW_STACK_BIT. A VMA_IO_BIT check is no longer required but that is fine as a hard invariant has been established that only kernel-owned mappings may set VMA_IO_BIT so the check is now redundant. Signed-off-by: Lorenzo Stoakes (ARM) --- mm/userfaultfd.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 949017e60608..ddf0a4a3d399 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1754,10 +1754,18 @@ static inline bool move_splits_huge_pmd(unsigned long dst_addr, } #endif -static inline bool vma_move_compatible(struct vm_area_struct *vma) +static inline bool vma_move_compatible(const struct vm_area_struct *vma) { - return !(vma->vm_flags & (VM_PFNMAP | VM_IO | VM_HUGETLB | - VM_MIXEDMAP | VM_SHADOW_STACK)); + /* uffd is generally incompatible with kernel-owned mappings. */ + if (vma_is_kernel_owned(vma)) + return false; + /* The shadow stack should not be written to by userspace. */ + if (vma_test_single_mask(vma, VMA_SHADOW_STACK)) + return false; + /* hugetlb mappings cannot be safely moved. */ + if (vma_is_hugetlb(vma)) + return false; + return true; } static int validate_move_areas(struct userfaultfd_ctx *ctx, @@ -2146,10 +2154,11 @@ static bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags, { const struct vm_uffd_ops *ops = vma_uffd_ops(vma); - if (vma->vm_flags & (VM_DROPPABLE | VM_SHADOW_STACK)) + /* Non-persistent memory is inherently not controllable by userspace. */ + if (!vma_is_persistent(vma)) return false; - - if (!vma_is_hugetlb(vma) && (vma->vm_flags & VM_SPECIAL)) + /* The shadow stack should not be written to by userspace. */ + if (vma_test_single_mask(vma, VMA_SHADOW_STACK)) return false; vm_flags &= __VM_UFFD_FLAGS; -- 2.55.0