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 4AB844F85D6; Thu, 17 Sep 2026 16:39:17 +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=1789663158; cv=none; b=WPXib7Z2HDMRLVyRUIEdP9w0VykKhgsgWfVP9wfPYrT+kfhnARBWQlJgtBSlJwThKfZfxOVslrUhyfGDJFoYaNSLYr2aAFIVc17CqiT4pG6MlA/HCX1OsXYrBXneTv/NILFrYaaesTOT1UNbybcF+Ss2GymYVeV71lDBNkJB8tQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789663158; c=relaxed/simple; bh=RaKyg3GqRiVqHvw/UDaaHvGcpLhQwigi+RNlsL2zffs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=uVDS/8fzWoxrsDTMaCAjaA1EM2kyZIl3i9VuSIxulaF5TQ0a1cblKQDxQtuy7OSsFnT0fbuG9rb4unphe1ZfTA/A/rjNvRKPLglv5y9uh5ID0yn3sZo0Hwa8g8SEf6T1etvmVV1m9JMh1EoOD6r+9qK9S2vnYnXwWByiwH3Ymo8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JuzlckQR; 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="JuzlckQR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2FFA1F00898; Thu, 17 Sep 2026 16:38:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789663156; bh=9WoUWUiccCZ5pmncdG/fVn1uDF622HEjGzqeAT5aHc8=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=JuzlckQR6v/NzH0mtru1XZ7iqyxCxBjrCwCFsUHW609jPCf8U6sfhyPJkkpToF69f siJ7N2NXwspDpQ5dJIIyLpRq7MwSgE3R3mqg5OrgAtBYXQZyoeaTTM2m6j28o+aBbX I7FSiMwxg1YdjTyYq2YbYkTvH901cTdfYaUc365eMr8X4iPtaA7EQGoTbcu8Y7USWP bzvY4XKh3JpReezKG88DwuCuMK1EFa2lyia7xTBCesd95C4tljlOVn0ygfLWln5b8m HFBw3K+lt5pgVgVgyTxhxlY5CZ9zPDN2L69fXPf9G/mWuVci/9xx+4Tz25j31d67md EUctPDbCJlXcw== From: "Lorenzo Stoakes (ARM)" Date: Thu, 17 Sep 2026 17:22:41 +0100 Subject: [PATCH v3 32/40] 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: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-32-4583d8a23bca@kernel.org> References: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> In-Reply-To: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@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 , Chengming Zhou , Michal Hocko , Miklos Szeredi , Xu Xin 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=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLWCB/OPPvVb8aRBlaPSTM6P2dc4rwuwDBzzqZoPX/27 rSo12wRHaUsDGJcDLJiiizPv4jvDxIJm9d5wd8NZg4rE8gQBi5OAZjIn1ZGhu/b9ztfWa90el/9 TetPvC5Nrbrrmvhtz33cqXTRuuHAHX9Ghi+axsy3Htr+lVOdM/mU0QoVzTe+TDpKZk8zz6fZScS KswIA 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