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 7EEF2539787; Thu, 17 Sep 2026 16:39:47 +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=1789663189; cv=none; b=bdx8W8klnpz1nHruQ/Tx5ueOqLBge7QdJemad2oyDOkSp75UxLJN6tPW2JQrrexS0ZeyE2wh1Hifj1TzjNZ+ailCrF6hc1fXz1rMPPVgNYiz+7R8rX6V/hbo2aFruHfTjDtH2bZasuvmf0qXT100j2TBC9LqRNlyG1Na8fGer7g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789663189; c=relaxed/simple; bh=73C/rtzFa+0ZWXqoblfAsIR57zB38R+k6a/jXJhy+os=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=EzGvfO0uL9zB2F6EkvP6VxDIDI92CKTE+Ep84eBnoSkvcsJWBQDuGFu4H3q0BKfHOtHW883NNcznda6zJcG2YFzndCV7oQTpOY5hKtR0ocfZLTSQBdtbQFU1MINiN2iF0P8Gw+s/9oJQr3Tp2t20PR9W1KHOhZ5n4J556Ri9Nik= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WXlzrcdv; 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="WXlzrcdv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51BD71F00893; Thu, 17 Sep 2026 16:39:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789663187; bh=Q7igvapfDwrm+6txgQcyn+RMKEShI1bTZhFDIgbQAbI=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=WXlzrcdvB27dNz/P8fXcUhO78TiBpsDAscSo6k7ve2SsKbAa1LfeACh5BlLu8aME5 vovXK74qJt0dDl7o3y8RQrcYpgG2S7MTHWgiZZ3VAercG9ZPudQZUvcNl4TkyHZGCM tmf72RuV4Uj6KLqiVvmMxxNCU1i/onR+4mI0XBGqKFnVIVtJIrGBrN1KWlndSs4bY6 d2yoD3NtHi3pm/PdGTsOBejNNPJwK2f0WWA6iyzUdjcZ/JggiiPSpvVYiVRZhUEiRW 5V3OUrBhNrca3ZxIfqAbo0cC/hqeLdOFO3Rs8Q2vxUYb/RK/kQyepsVHmJZxltTgMf BGQ3vFMrSxvyg== From: "Lorenzo Stoakes (ARM)" Date: Thu, 17 Sep 2026 17:22:42 +0100 Subject: [PATCH v3 33/40] mm/madvise: use predicates for madvise(..., MADV_DOFORK) 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-v3-33-4583d8a23bca@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=1318; i=ljs@kernel.org; h=from:subject:message-id; bh=73C/rtzFa+0ZWXqoblfAsIR57zB38R+k6a/jXJhy+os=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLWCB/Jbo/i/9WleylGkUOJSVnsF+vBqDUTc/O1pRKZh PutF1d0lLIwiHExyIopsjz/Ir4/SCRsXucFfzeYOaxMIEMYuDgFYCJR1Qz/LCTWeyxN8uuO+Dfh 1tnvF5ZZdbjMPmw38/uBjzF68geEIhn+RxSZL6s5IHRKK+JivrVjwcXdHhLOe3V2LJr/dOd1rtn L2AE= 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 e15973292f94..1af82b044d23 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1565,7 +1565,7 @@ 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