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 CF6DC519E0E; Thu, 17 Sep 2026 16:29:06 +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=1789662548; cv=none; b=WYEKOQ4iORPvPGq2v+lC4VnWx8GxP8LQhVWoKrKNN7ph5yiKPJl/ENdjORwsMFFpvzch0MBdGFTVkIjsaRHErVgw5RMFjsVMZJ6iJ4ik+TEReXXviVAD3OhR2Ai6YZLk2dfULs/TIes4psaUzU6gxQ26d5UrwneRdr49p8gqmsA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789662548; c=relaxed/simple; bh=X46vXp5xg8nLI6IG+V/Ab12M7pEZi9uJqKdEh54QAaM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=kTi+wRodsrliP/eWx6waSKOx1dibr6/4KfMu9Ne+UlZyiL5206KENY7W866ZJEfP40VtFgtTWlyGyKYTokqJlQOFnkbVBF0yw334wuZoMRaj4vzu8wxeXw/u+qhhTmfwQWZiDsmZrTzKuZifpvoHojpHGmaQBHJs6PAnuno4Hbc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HypnJxB5; 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="HypnJxB5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9CE821F00898; Thu, 17 Sep 2026 16:28:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789662546; bh=qivR91Lb5/7S8p3yp1PCCxRNqvAnmMyhYSRWXpH7C6E=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=HypnJxB5nIvhdu/4lyn5V2mzaHKgTstFT3NwAe1e5+ZqghSmo2Hj7mjOK5CoYdPTx PARyOmBlb+YzHiiTbiLYqT+yzZYIAG1LQnY4c8bg49GVruVJRAH7a6NjefXjko9YKe 9r3cgnvRiFC1xOnahoCdXU8zbumCPYOfyFGs4CNmNaflrU5KmEGeqQTv6WftryliCv CRL4rfF58Fu402gQsvBPnH8MGc7bjyLyzMq12dc+KlyivUJWTpRdYhUPAbO0MiuYkb PKD1LFiaRtReUNXpDsNBS9Zzu0GWIjj5xX+3hcbxhXXBLaGJKY68gTeOSmcn1LIJG2 /RIfIU50StAcQ== From: "Lorenzo Stoakes (ARM)" Date: Thu, 17 Sep 2026 17:22:21 +0100 Subject: [PATCH v3 12/40] selinux: reject writable opens of policy file, drop mmap shared/write check 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-v3-12-4583d8a23bca@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=1924; i=ljs@kernel.org; h=from:subject:message-id; bh=X46vXp5xg8nLI6IG+V/Ab12M7pEZi9uJqKdEh54QAaM=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLWCB/4+lNC4kLT9Xfr2cNNWOx/bZBxCA3lc/ddrff0/ HctqbfsHaUsDGJcDLJiiizPv4jvDxIJm9d5wd8NZg4rE8gQBi5OAZiIwDKGn4wMy14xmso2pPDv D3n68b3oKp3jKyvnaKX67T30WCys7jQjw36LHf1Lmqed1JoeuUrratDu63IFu0+J/2G76s1hYfO rihkA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 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. 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. Acked-by: Stephen Smalley Reviewed-by: Jann Horn Acked-by: Paul Moore Signed-off-by: Lorenzo Stoakes (ARM) --- security/selinux/selinuxfs.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c index c7d91476971c..545a6f89f9e7 100644 --- a/security/selinux/selinuxfs.c +++ b/security/selinux/selinuxfs.c @@ -340,6 +340,9 @@ static int sel_open_policy(struct inode *inode, struct file *filp) struct policy_load_memory *plm = NULL; int rc; + if (filp->f_mode & FMODE_WRITE) + return -EACCES; + rc = avc_has_perm(current_sid(), SECINITSID_SECURITY, SECCLASS_SECURITY, SECURITY__READ_POLICY, NULL); if (rc) @@ -424,14 +427,6 @@ static const struct vm_operations_struct sel_mmap_policy_ops = { static int sel_mmap_policy(struct file *filp, struct vm_area_struct *vma) { - if (vma->vm_flags & VM_SHARED) { - /* do not allow mprotect to make mapping writable */ - vm_flags_clear(vma, VM_MAYWRITE); - - if (vma->vm_flags & VM_WRITE) - return -EACCES; - } - vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP); vma->vm_ops = &sel_mmap_policy_ops; -- 2.55.0