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 7A56CC5DF81 for ; Thu, 20 Aug 2026 17:22:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 93EE26B00A0; Thu, 20 Aug 2026 13:22:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8EFB66B00A1; Thu, 20 Aug 2026 13:22:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7DDB66B00A2; Thu, 20 Aug 2026 13:22:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 52ECE6B00A0 for ; Thu, 20 Aug 2026 13:22:14 -0400 (EDT) Received: from smtpin07.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id CFEC216023E for ; Thu, 20 Aug 2026 17:22:13 +0000 (UTC) X-FDA: 85122316146.07.ADBFD79 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf19.hostedemail.com (Postfix) with ESMTP id 2ACC61A0007 for ; Thu, 20 Aug 2026 17:22:12 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Dmt9pdtA; spf=pass (imf19.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@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=1787246532; b=wPiw0Xz7brHyMjDd51Kc/fN7sxWj8rxYj3rDlJRoW6s6eB8HIispGNodDbHjwaBVhxBypm zJVViAVrT2vdLWzUoQd//xh7s6MG2Tplzx7dG7afUdsPRpmKgFj45csLV6zs5Uk19QQmhe +H5tRD7RuhMdQif+4WlRbbiBQETpqfY= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Dmt9pdtA; spf=pass (imf19.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@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=1787246532; 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=exJPVe3Jxp/tmieGVsSX37DfT17fcVo21V6QONpXeNI=; b=fR0BEohPm3oFp3sshXmGPRbCjfMk8AH3rZZrQWI8fDIzyBjUXOIl4lBuUyajsZJF/0a0qM hghqEJ7yPbWIHYBKKCuJ/vIpi9gh//tZpDwNmMqPP3E+BUZt6aWXkSRt6chhpQROYuBe8A OdOt3V8HYzNT3o2CHuHEztE5U164w6c= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 1078160A61; Thu, 20 Aug 2026 17:22:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6F0601F000E9; Thu, 20 Aug 2026 17:22:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787246530; bh=exJPVe3Jxp/tmieGVsSX37DfT17fcVo21V6QONpXeNI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Dmt9pdtA3/p613ajbp7hmcIJVgS2TQHeLlgtiu7vWSUu1MMYvXjYQeulyuXMoum5D 8AOXRqGykr6pbXsXdAyaggpB6RzXclohx0UgNkZ9FadBrjIZPemr18KbQY5D8WaSzO wMHArm6zeACTYN0mapGpEKCV2j1FDX/iXRvHjv9J1hp1iupsbFzZRPsCBy8OmOFLLV SEYJnGn63SfMFUCMdAqtpTugUpKyAbqNpF1s+ANapL3eoIj0+gRjkMnpcpYBWf/ka5 W5HOwKYpiBg12FBO8ccNmqHyb3aogFJSUjj7REPK5dzNAJLdIXJlAA3RZkAOEsxqoK jC9WPfSZ4VPIg== Message-ID: <741a833d-6889-4ee6-9322-d6a3a8b95893@kernel.org> Date: Thu, 20 Aug 2026 19:22:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] proc: query LSMs for introspective mem access (if PROC_MEM_FORCE_ALWAYS) To: Jann Horn , Paul Moore , James Morris , "Serge E. Hallyn" , Stephen Smalley , Jeff Xu , =?UTF-8?Q?Thi=C3=A9baud_Weksteen?= Cc: 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" , Lorenzo Stoakes , Vlastimil Babka , Pedro Falcato , linux-mm@kvack.org References: <20260818-selinux-pokemem-v1-0-90cd2357ee05@google.com> <20260818-selinux-pokemem-v1-2-90cd2357ee05@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260818-selinux-pokemem-v1-2-90cd2357ee05@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2ACC61A0007 X-Stat-Signature: f1d4a845k5ka3co6if5dqjnzuhqx7np5 X-HE-Tag: 1787246532-845601 X-HE-Meta: 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 hmm7Ypsc RVsUsNuPCdtFwWYH+2k32bOc0c37GfSRcvTnsvFd7jIkhLGqe3P8ZCSwfbM7VmhD1NtC8JXp4qyIZl9PVrpV9YeRoYahBH9+yTiaakO8tC+cgfyVTnpxuT+IAAnSdfosmVVTOk+PHDpya0ZpPS9241tC7qbcq2ANKWBAOSlG7yGK3c2NX91taTJJHK5O9BRpdhI+JtoUS9CfGODOnQW4/BgxNM5Hq7/cgFWmpVNKYSUatiNPQJ3YwjDmj4mSRVZ1Lk/enCUzp6NyYqCqYPX5cDgxTm9cspBqMJSl58lLXfOc0IuHMBw4rBOOEbVih43AlVcd/z7OE4U1yWtlzY9Yx1ln9SaKn7nYABR03K48MvB2eayyQkxPGRKILDlbCnsuO5EejK6D8aSr4yW9AcBYAdOz7hw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/18/26 21:51, Jann Horn wrote: > If the system is running with PROC_MEM_FORCE_ALWAYS, LSMs currently have no > good opportunity to block a process from overwriting read-only code in its > own address space through FOLL_FORCE writes via /proc/self/mem. > The security_ptrace_access_check() LSM hook is bypassed when a process > opens /proc/self/mem because this is considered "introspection". > > This causes a hole in SELinux EXECMEM enforcement, which tries to ensure > that a process cannot create executable anonymous pages. > > PROC_MEM_FORCE_PTRACE prevents that and ensures that such FOLL_FORCE > accesses are only possible when the LSM allows ptrace() attachment; but it > is unclear how quickly PROC_MEM_FORCE_PTRACE can be deployed in > environments running lots of third-party code, such as Android. > > So, introduce a new LSM hook that can forbid FOLL_FORCE specifically for > such "introspective" accesses. > > Signed-off-by: Jann Horn > --- > fs/proc/base.c | 6 ++++++ > include/linux/lsm_hook_defs.h | 1 + > include/linux/security.h | 6 ++++++ > security/security.c | 15 +++++++++++++++ > 4 files changed, 28 insertions(+) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index bec6197329dc..3dfaef49bb70 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -851,6 +851,8 @@ static int __mem_open(struct inode *inode, struct file *file, unsigned int mode) > /* private_data for proc_mem_operations */ > struct mem_private { > struct mm_struct *mm; > + /* Was the ptrace access check bypassed due to introspection? */ > + bool introspection; > }; > > static int mem_open(struct inode *inode, struct file *file) > @@ -864,12 +866,14 @@ static int mem_open(struct inode *inode, struct file *file) > priv->mm = proc_mem_open(inode, PTRACE_MODE_ATTACH); > if (IS_ERR_OR_NULL(priv->mm)) > return priv->mm ? PTR_ERR(priv->mm) : -ESRCH; > + priv->introspection = priv->mm == current->mm; Is the feat that the fd could be passed to someone else that would then not be detected as introspection? I'm just wondering why we cannot perform this check in proc_mem_foll_force() and avoid rememebring "introspection". -- Cheers, David