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 553D42E06E4; Tue, 25 Aug 2026 13:42:46 +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=1787665367; cv=none; b=dHgHroqwG8gvRh8yVPCBfKJjqHQ+Rki+cMUJxXB1UdRGLx0Wmnc1P0ReLBp3Xn3dOVTDvpZIpLvSikgFdvpOOvq3IZgJzL/EU8fUu5mGE+3TgPHfOURD5/84SLDcPUm33NzVEsVcK+FUxqom5dNhRnPHGbhtKWd0Sub9V6j4xLc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787665367; c=relaxed/simple; bh=RAeO6nyzsto4THOPII8Lhn2KD/5f7sb4XDD8FP4is4I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i5pRYa0DkwsnHNM50l31T6iyRAZaQqWATCe7kvFZh6RFxh7NvZchRUDb+vPehB9JhbYumvH0c07CTcETfIVUOHxVv7cES1+J+rb6NIeKEBYhzlaYLRuSljuNk86V1jn83mY/isRXSSFLBdJR35JBx5Kbj83TQL/r+H+OEZt/UTU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GhBex4Nf; 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="GhBex4Nf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52D931F00A3D; Tue, 25 Aug 2026 13:42:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787665366; bh=RAeO6nyzsto4THOPII8Lhn2KD/5f7sb4XDD8FP4is4I=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=GhBex4NfYPWHAIis5wTwo0tQjKG0lEFiWWqT4AQg20VnPw65oPAP/ZjSBF87ydOy2 Dj5OuprDFDH9S2asvTA9JHcSPvk0+8xggfaitkr3FK2GGKPGPl5xETSIR0dVpWvAfC cXQWCNYrMYu/fgRgUR5Zwg91ussB2GAA8VT7l1VZgOatlF0HnMgp+XrUnGGSYJYzOO Ckv9lrJOtp389yjaUjC80xmQDUkR/SqEJd1GkGSkqmgmPzC12z0nNoHBt6esAy6l9Z CiXZuotZstCJD+E81JYGtDcC/6JESfGN+93090PCKU9OCWimw/uqBIYF+n9m7Re59L RwiIpFdanGSRQ== Date: Tue, 25 Aug 2026 14:42:38 +0100 From: "Lorenzo Stoakes (ARM)" To: Jann Horn Cc: "David Hildenbrand (Arm)" , Paul Moore , James Morris , "Serge E. Hallyn" , Stephen Smalley , Jeff Xu , =?utf-8?B?VGhpw6liYXVk?= Weksteen , Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, Ondrej Mosnacek , selinux@vger.kernel.org, Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Pedro Falcato , linux-mm@kvack.org Subject: Re: [PATCH 2/3] proc: query LSMs for introspective mem access (if PROC_MEM_FORCE_ALWAYS) Message-ID: References: <20260818-selinux-pokemem-v1-0-90cd2357ee05@google.com> <20260818-selinux-pokemem-v1-2-90cd2357ee05@google.com> <741a833d-6889-4ee6-9322-d6a3a8b95893@kernel.org> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Aug 24, 2026 at 07:43:02PM +0200, Jann Horn wrote: > On Mon, Aug 24, 2026 at 7:33 PM Lorenzo Stoakes (ARM) wrote: > > On Mon, Aug 24, 2026 at 07:06:04PM +0200, Jann Horn wrote: > > > On Fri, Aug 21, 2026 at 8:52 PM Lorenzo Stoakes (ARM) wrote: > > > > The sharing a /proc/mem fd seems like that's a pretty dumb thing to do in > > > > general :) but I guess you have to protect against that. > > > > > > Yeah, it's a kinda weird thing to do... > > > > Yup :)) but I guess we have to account for people doing weird stuff... > > > > In this case (I do mention it in a reply elsewhere I think) it does seem > > like perhaps you should separately check for current->mm != mm of (what was > > originally /proc/self/mm)? > > I wouldn't want to do it for this access check, since that could lead > to "confused deputy" problems. I guess if it got the decision wrong somehow that'd be a problem? Or wrongly OK'd it on one level but then that led to the fd being passed on assumption it was OK to do it or something? > > > Or at least it seems like a crazy thing to be able to get full access to > > another process's memory (that it... gave you though). > > > > Anyway perhaps overthinking it :) > > Hm, yes, though I guess that is kind of orthogonal. > > For what it's worth, SELinux can prevent such things happening across > domain boundaries - it enforces that, in the SELinux ruleset, the > process calling read()/write() on an FD is granted FILE__READ / > FILE__WRITE permission to the file's inode. Ah OK that's good that it's at least possible to check for this class of problem so the rest is moot then :) -- Cheers, Lorenzo