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 CDDC747C104; Tue, 8 Sep 2026 20:17:42 +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=1788898664; cv=none; b=YIE4ztWcjChMpQK69nr8teIywUYKzWtjIM5g8/QMlcm8o1FM5Wxs3id9Baou4WGi2I9bkV2NmuBfQlD18m14a5gd0GscmknR4xY8GTZto0E/SaZIfzXT/bkFaqRPJRk/DBnfd6a9T5lCpM5XMKfIibOymSE0IKNnbqtdrUAu5WI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788898664; c=relaxed/simple; bh=TpPN2uIwyk7OPd2HBI4HDHxlc10ZpBuX2afWbalydvk=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=iM58ygA7m5Ig92tkuXx1XRtV5RYJhx2do8a+bA+raK6rpidcybpPabQlqfvQJZT0sQMzWWZjfreElw7KODSdmmhkLViMTsOZXn1u7gTCLTGpuQs2en4wFM03xR64H/1O8sSE4y2tLMQRGmU1QaW068S3HwZqoMLrB9uO5gG/8OE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nSWBV92L; 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="nSWBV92L" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3AFED1F00A3D; Tue, 8 Sep 2026 20:17:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788898662; bh=fq/fqooLp6MfqSbPhzdOUvBF6Y5t6h1fABLuyvNgM4c=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=nSWBV92L+8t85kwuXHhkDdHjHxkPeSVQxnQMn5LDdjW/GH3RVqyylhr9uF/rq7fMw IfsOvxIPVuLYZAxIct2QzMu04i7HxvW5irZq3CgmmtoyeP8i8aQeqoI6bIukQ/2N5h XprLc3jpyjfbL5Gn4wzXeKKiM9sllVEhyrfcl9XF77WXNObvHKajzVmpIe5dBsd1Ko S7q6g3Te9Bt3hrNbZYTCSM8M6O0Ln9y/8KvHRS5h+yAbVSkOaWNKBwUXyDOx0f4iBz t0zSmYE9hyM3PIZ9eCfmiKanYIC9dhvvc33E3z6yfYVF2D54QxIabTvgmvGOdILKjf tqlk99+loBPuw== From: "Lorenzo Stoakes (ARM)" Date: Tue, 08 Sep 2026 21:01:36 +0100 Subject: [PATCH 32/39] mm/madvise: use predicates for madvise(..., MADV_DOFORK) Precedence: bulk X-Mailing-List: linux-trace-kernel@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-v1-32-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=1318; i=ljs@kernel.org; h=from:subject:message-id; bh=TpPN2uIwyk7OPd2HBI4HDHxlc10ZpBuX2afWbalydvk=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLIWZG71OZ8YG6oUvPbDhZWKFe1bWV9uWZA4/eGCU08LV +n9imKZ1lHKwiDGxSArpsjy/Iv4/iCRsHmdF/zdYOawMoEMYeDiFICJ8Bow/OGw4Fc81vZa3NGh ZplwvVTyy0oLmQjl/ekSq1+lq1+acImR4WftM4X62JoP/VfumMyvvPKl3WmxvsPbdJG00K75q8P mMQMA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Make it clear what we're blocking in MADV_DOFORK. Previously we simply disallowed VM_SPECIAL i.e. kernel-owned mappings, fixed mappings and VMA_IO_BIT. Now the invariant is established that only kernel-owned mappings can set VMA_IO_BIT, the VMA_IO_BIT check is redundant. The rest is equivalent to testing for a kernel-owned or fixed mapping, i.e. exactly the same check as whether the VMA is permitted to be merged. This was established by commit 0b2758f48f22 ("Require (reasonably) normal mappings for MADV_DOFORK") containing my hands-down favourite call out of all time. Express the same thing differently - if we wouldn't be allowed to merge it, then we aren't allowed to manipulate CoW behaviour on fork. No functional change intended. Signed-off-by: Lorenzo Stoakes (ARM) --- mm/madvise.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 0fc31835fee1..f805a4876c87 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1400,7 +1400,7 @@ static int madvise_vma_behavior(struct madvise_behavior *madv_behavior) new_flags |= VM_DONTCOPY; break; case MADV_DOFORK: - if (new_flags & VM_SPECIAL) + if (!vma_can_merge(vma)) return -EINVAL; new_flags &= ~VM_DONTCOPY; break; -- 2.55.0