From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5B563C88E4C for ; Fri, 11 Sep 2026 10:13:57 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4hh9PH1rmbz2yFj; Fri, 11 Sep 2026 20:13:55 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip="2600:3c0a:e001:78e:0:1991:8:25" ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1789121635; cv=none; b=n5wa5SBR4XaXlRyczvV0hjM2Ge0Mv4Sqr9cu8WeHm+SvjW7QsmXmhOcwIvaAyCopCm2TC/xkEgAgndLf95qjv/mEPr8JRPJwaZXxXN182QrcXgUlx0u2r1bIYvOm6pZX6MvWNoCNUhtHHDCnRh7K3rsLB1ZDm2slZhKvv4WlPVo4cOC/3B6fL9PRUKcJB3TiuEK7m11jLyf/ZyfYi9ZDzlGRBfILBywpLLMM2Fp6OQ6cwX0/v+6cMVPU3R9VOoCXo6agtZR3WzJfNjjt9+ytjtDazsAiawJKuK5K/gMn79CfsMRRIJIzYZ44ynHiAKTu5n9zmlDbdyu+dtUgr7ZX+A== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1789121635; c=relaxed/relaxed; bh=AJ4osXGfnva+GsW9Xj6wSlPvmOYx8+Z4McGwoEWWU6k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aETlqYeSwdEuM4J6/u83F6x52fOJXfYMst4VS3y4UPGP+jiUJu4OcZIksu8MpmYZux98p9TQmGiMgFMMDftjqlXQaR5n2MZEWcq0BcrEignzQnatP5boMmEhWCBjrza5EZUHE9/885yPRD1omBXCVCoMqzSQV/O/DwbQMQuknMGoKwgQAu4Er5quQK3XUlmNtwsWTSqH2bzYRqp1eXaBYlKznAgZAJwfyj9NI/kSzroAjmCptWJzGkCzet5eTGv01XSBFJBy8iFrcdjyjlniTWzT82DBekLicKhRvqzEmVe1wddx8RZfda986pTyzHcl89pyWmUpTmThWAgtPBisdQ== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VXiIsYXG; dkim-atps=neutral; spf=pass (client-ip=2600:3c0a:e001:78e:0:1991:8:25; helo=sea.source.kernel.org; envelope-from=ljs@kernel.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=VXiIsYXG; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=2600:3c0a:e001:78e:0:1991:8:25; helo=sea.source.kernel.org; envelope-from=ljs@kernel.org; receiver=lists.ozlabs.org) Received: from sea.source.kernel.org (sea.source.kernel.org [IPv6:2600:3c0a:e001:78e:0:1991:8:25]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4hh9PF6NGQz2xpv for ; Fri, 11 Sep 2026 20:13:53 +1000 (AEST) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 9E893432D5; Fri, 11 Sep 2026 10:13:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88F4F1F000FF; Fri, 11 Sep 2026 10:13:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789121626; bh=AJ4osXGfnva+GsW9Xj6wSlPvmOYx8+Z4McGwoEWWU6k=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=VXiIsYXGW7V+CUC2hoUUxshBtk//170ahXby5qOmnHCTEG6nprU1IS50u25G/fRQk sf9ytH2Ce2iGqonEAUfAmBNxEiX0H5gDZvz851NX8EhIuDaWSIQBlPZWYHnVma0aGj blDmI4LY1KM28dzcRxXSp3rNd+ml+k1Jf5jXcr5BNdmFsP+f0lE+KyInKD5utrTv18 j0kWa0ZAaMlc3Pw4wRDO2h4SoWYRal6ZvW3YmHkVxX6gQf6/JqWhQp1QSVXE2Kca+2 BYYLTVktrg9Xqy9CLQ0dyOX4enXiqnPzEjwUfsC5vJviK7A/gYwNlJA1GGOz2i3bhy SIFHvCnClRnig== Date: Fri, 11 Sep 2026 11:13:15 +0100 From: "Lorenzo Stoakes (ARM)" To: Jann Horn Cc: Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , 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 , 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 Subject: Re: [PATCH 11/39] selinux: reject writable opens of policy file, drop mmap shared/write check Message-ID: References: <20260908-b4-mmap-prepare-vma-flag-sanify-v1-0-dacf19cce22b@kernel.org> <20260908-b4-mmap-prepare-vma-flag-sanify-v1-11-dacf19cce22b@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Sep 08, 2026 at 10:22:20PM +0200, Jann Horn wrote: > On Tue, Sep 8, 2026 at 10:07 PM Lorenzo Stoakes (ARM) wrote: > > The policy file has no write method and is exposed read-only (S_IRUGO in > > selinux_files[]), yet sel_open_policy() performs no open mode check, so a > > CAP_DAC_OVERRIDE caller can open it O_RDWR. Reject FMODE_WRITE at open, as > > kernfs does. > > > > The file can then never be mapped with FMODE_WRITE, so do_mmap() always > > clears VM_MAYWRITE and VM_SHARED for MAP_SHARED mappings and the VM_SHARED > > check in sel_mmap_policy() cannot be reached. Remove it. > > You should also be able to remove the sel_mmap_policy_ops.page_mkwrite > handler, which is only for shared-writable faults, right? Yeah I think you're right, though I wonder if it's a bit out of scope for this change as it's focused on removing a VMA_MAYWRITE_BIT clearance for a non-kernel-owned VMA. So maybe one for a follow up? > > > This also stops sel_mmap_policy() clearing VM_MAYWRITE on a mapping that is > > neither a PFN map nor a mixed map, ahead of the core enforcing that only > > such mappings may do so. > > > > Signed-off-by: Lorenzo Stoakes (ARM) > > Reviewed-by: Jann Horn Thanks! -- Cheers, Lorenzo