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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 42211C61DBE for ; Tue, 25 Aug 2026 13:42:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5B7266B00CB; Tue, 25 Aug 2026 09:42:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 58E8F6B00CC; Tue, 25 Aug 2026 09:42:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4A4406B00CD; Tue, 25 Aug 2026 09:42:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 22CBE6B00CB for ; Tue, 25 Aug 2026 09:42:49 -0400 (EDT) Received: from smtpin12.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A1DECA2B20 for ; Tue, 25 Aug 2026 13:42:48 +0000 (UTC) X-FDA: 85139907216.12.6F26E32 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf09.hostedemail.com (Postfix) with ESMTP id E8CF4140006 for ; Tue, 25 Aug 2026 13:42:46 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=GhBex4Nf; spf=pass (imf09.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787665367; b=z/0qnLAZwOs/YA4tzcEEDmVZAygTuMPZKfw9FW/JFmqKj+3eQ/3SuJ1y8KjQmvCPOi0SMK ofb6DyAxwJ6eN56U9AqglazGRZq5BrPOPxCxiE+8I9mOxYYCfTR2XsSc9+/yVrHm3ex7yz 36/v5NPnRS8ni8mPBOuBMG8/zgg0KMo= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=GhBex4Nf; spf=pass (imf09.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787665367; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=RAeO6nyzsto4THOPII8Lhn2KD/5f7sb4XDD8FP4is4I=; b=v3HvUSlI6Tr2KojYDVgExOsX94kly9hQTkX2QynNX/ayqPQ8wMnhgnR3sAlUfgzAdqIgih z/kKaWsUmuLErP0i9/pZj8AEwNc7XyOkgY29FdHbmjK2uYHIFTZuVbt+5qDRKyNotHbCZp hmlmAyJo57ukToGZvVV26wl2QR6L8lI= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 1771841A02; Tue, 25 Aug 2026 13:42:46 +0000 (UTC) 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: E8CF4140006 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: an9myq7z4ikb575fto4w39tto6qeheoj X-HE-Tag: 1787665366-528986 X-HE-Meta: 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 y8Wl5UCV 75Ti9yL9sFx9em6siluynty4zF9Bs10eqG3uBvDbwN0N3/TyKJy65Ti9lXnKIiPBON5Cwnb8Un+E8pd5mAL3YKHHA07RVU9M1b5Ofo3Q8xUYjxilNFORuIzfs3NphGRPh6hJYvzV4+1LhVnzWGWD71Bh/a+uZbUvem4WXht/3J4PI5vFIe+Wfo/XbrhMpikQ2be7J9doqEzsdjmECUiUVumgqj+np1OMdtX+9GBn26ELtLGWEPNKFqp1RWfosk0WIw+ixdfox5Lcu2PX8AzABCB3Uu2U0neMmDEVFXJKlzsVCQnMZNYsW7/A4LQtR0cFn/nHnWivxDaAnCyBBclSNQbWpKG11eq+QtFiMqMa1Kd2EH3r/h9Vk+9Isp2aiWgJQpKd2qEv/dFbhNwpZAadDumRwf2a9VIU0IPYL447zX0/f1P8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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