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 E91E9C5DF89 for ; Fri, 21 Aug 2026 14:19:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0E9B26B00A0; Fri, 21 Aug 2026 10:19:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0C12F6B00A1; Fri, 21 Aug 2026 10:19:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EF2F56B00A2; Fri, 21 Aug 2026 10:19:04 -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 CF5E86B00A0 for ; Fri, 21 Aug 2026 10:19:04 -0400 (EDT) Received: from smtpin03.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 5DB7B1C00D3 for ; Fri, 21 Aug 2026 14:19:04 +0000 (UTC) X-FDA: 85125483408.03.5289BDC Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf28.hostedemail.com (Postfix) with ESMTP id 9E5C0C0009 for ; Fri, 21 Aug 2026 14:19:02 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=EjZSYAWO; spf=pass (imf28.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1787321942; 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=u2XbnGzR4oklypPgE+Viv5JNUn/D8iY5cwkY2Kqvw4E=; b=bRU5sSjGCVqiVeAbyMCGLFgLV7HQ9Z1UzUqDrYhzyHUhZcXK1RZJCCG4dlVQ8XIPWyzcY1 z48/gwhTvxxVvuLCNEc2cHhFhEmv5na3zY3DFKFw1B7hNia5bS/QL9CdZvL74SNdLLavVR YCJMEEKZxUHmtmZl/44fQBR64xN00Y0= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=EjZSYAWO; spf=pass (imf28.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1787321942; b=FIePNWuWIzpfN+2byzzRlSRMMDba5BweAQWZuRJMJSXDaIpVPUv4pkK4Iq9Utl+7bvNioI 4s31iZq26QLSWORg9zcpmbGyg18WXZY9HH0L04b4CbllKYVzqaU/+BqGArcp9Bzu3Z/sW9 LS7qpZ7ztK8kdPe5mCjTH//OEEPfEpI= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id ECF1843384; Fri, 21 Aug 2026 14:19:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 841651F000E9; Fri, 21 Aug 2026 14:18:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787321941; bh=u2XbnGzR4oklypPgE+Viv5JNUn/D8iY5cwkY2Kqvw4E=; h=Date:From:Subject:To:Cc:References:In-Reply-To; b=EjZSYAWO28454RqSV7v89nBk8+YcOGyf5apbjjM7L2GvqAzQasrzCMMMPrPqh6tN2 kRkIwcYM3KXd4a+eGEgaAWwNlI2c8Y/h0qkgIHqXQpCSlALAxzpd0dvHnfUQMALz9G Ru6tS0xXakGh3n3iyyQu9LPwr0J3OsSMOLtLQMOlDhR1sNYJRUWUQcBDQ8gNrGZAax ILBqWcxTxG9RrLGzzIIAaUFx5QDCqQn8LBEJIBTzQLpdUcdLNhT+sUmmzLFINod50N uHQSN1V8PHPDs2C3P8ltB4+y8NhkRl3G1uNFasRFtBVjD6wXe1GDFLFCotx11glIuO KpEGF8Pbq8DDA== Message-ID: Date: Fri, 21 Aug 2026 16:18:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: "David Hildenbrand (Arm)" Subject: Re: [PATCH 2/3] proc: query LSMs for introspective mem access (if PROC_MEM_FORCE_ALWAYS) To: Jann Horn Cc: Paul Moore , James Morris , "Serge E. Hallyn" , Stephen Smalley , Jeff Xu , =?UTF-8?Q?Thi=C3=A9baud_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" , 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> <741a833d-6889-4ee6-9322-d6a3a8b95893@kernel.org> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: rzxm1q9q3ah8s1fojohj8pspmi4t74r9 X-Rspamd-Queue-Id: 9E5C0C0009 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1787321942-394071 X-HE-Meta: U2FsdGVkX18FTxM7fuc8beK6G5eyfcjf32s0G/iqY/FY937VTQT7R2JAVbcdIay0bVOcombGTg8xbpqXWrzRWkpXdCCNM66jMSeoz4J7l6kN735B5IA3ljKc921KxtMNdACUEwIrZls7eLn1LiDraaqL6w6E7+2w8g8k69wOV63wo63X1/gR71tgtRQ58iSopMps/yr3vDg3MZua+iukSfF8ruB6xirA1Qv4pBOkMdl0QNkmtGblRuX+iiSzE0MBwZXDV82QuiLkjgfGZHqCthWPQCO9WiRRVu5BfcnAQlqlhfTxFfS4g10GybnHbwkCj5rZZ9oC4/wTVW+jRu7eDNdc+a5Z7vyjbvAMzxO+2i0KaoNdabHrV2OUZg/bpt/ejCDlEn3+Zi/PWoXxtpe6Wha1dZuB1y6VuPJqbHc1vNJ8Qi0PFOLQI48dPPiD4iOEz7NSPdKeJKpBjQ/KWMIQMjvnVmt95HWcZh5jILwRrepZv2lLuZvGWfLK4Z4it7x6/xfuHgUOoAGqoitJHC2WuUjl61z6Br3hJg1WeGQ7y9BDaGQZzeFqZPqeSybv3K7jOyLJ8rtiHsZzpgWcRE4D0t0/Yj5HWu8VimlJvAtVbuX+FrjVM5imZ9/oprlQv04saIxfrLpJRip4OX0STxQubKxOA9p55IA3o12NCZuuqYhiummkdjGjWFoIFDxCY82IFsDrWXrMJ9f79QO1i+qbR580UlG72gFkVI0Sf4EKx/T6/cvrD8/Y6fHRJzU5PxxUKqxFRgszZgFevle+syWh0JUxduAOO5DRq5BakMt9e5bvlPR2u9uL/WtETjsfEhuGxQtae0ejDQ8NdMdSHOCuKU3bbwW14j6uDzgva/ZPmbRD49DD9tWkvCNGHm8hytGcpzhAELdVZ+zVP9P6U/6X8mrkzytruwjCOg6H4Mf4jpLJmiI1usbqdKzJzrBAFCmvPZcoofmjYbq5K9YBe2l caPA5KpJ KMTaf7F9v9A/Oanq9kKjXlz+fl11hHG7vXcod8moPdCUUw1iT/NI4bHJTJTPsfIbDZn5AZwdeOHrtl5se5BPza0tqTeeTKVwe0pb5O+M3vpcXw1XkJo6SM/SsnCheDz5LVWpXHukUl3pkY/JMMgoydDny7V3fOtFIG4c0NQIVu6oRJyW7K+fU56TyHiELh9q+9DAS1VDYzP8u7OfFT0SUn5SdqzSxbz5nVqH2yr0QeBTTZEZS+IASDTJ4JgAPtzJbPnhuGhTSiQM5Dd5AENaORds2GYm83XrP9W0QLYj+x/3Al/m3Ir9n6bZ5ghxmGfR8ZriUG/sJKOViIiL9ipSBo8KijPVVaYQmK2zpTesXDJT8NcZQ5CTud214i1N+y+e7/YIf3pxHTJreKjmK4zbTk/mdcgG/Mrljl3Rz77oJvHBFIBydfA7gVVwFGE/0+JDu3h25dInIy28SLA0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/20/26 20:44, Jann Horn wrote: > On Thu, Aug 20, 2026 at 7:22 PM David Hildenbrand (Arm) > wrote: >> 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? > > Yes, exactly, that's the primary reason why I did it this way. Okay, would "opened_by_owner" or something like that be clearer? At least "introspection" is less intuitive for me. -- Cheers, David