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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D6DECD1284 for ; Tue, 2 Apr 2024 10:43:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A550B6B0092; Tue, 2 Apr 2024 06:43:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A04856B0093; Tue, 2 Apr 2024 06:43:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8A4E76B0095; Tue, 2 Apr 2024 06:43:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 6CBA36B0092 for ; Tue, 2 Apr 2024 06:43:31 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 03C6DA0EC9 for ; Tue, 2 Apr 2024 10:43:30 +0000 (UTC) X-FDA: 81964255422.30.E154EDC Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf15.hostedemail.com (Postfix) with ESMTP id 8F095A0012 for ; Tue, 2 Apr 2024 10:43:28 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=TrfD3g9L; spf=pass (imf15.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1712054608; 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=/zBpNACLXUrqP92by+X1aP2sLL3r5R2IUOWqrDEJp1g=; b=WhsoV1ebD8/VNSccv8Gs/NufyJnMRGZElakfHyB1+NEWeDGoAsImi5eShG+khhBoBvr890 rQIfF16kTGxLiQDyma63MegSU5i3QEQLjFsZtSG47hk5ELLmsxUbLeHljPpViwxABl9GV5 cryfyeG8331zRe+LK484JCTuZej+2b8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1712054608; a=rsa-sha256; cv=none; b=rf267IlDsQxIKOsZIR6qd58Z9D5o2SLPw7eo7S9sUWnpya8Bnthe6SBRgDX4BhYPAC018L yzrBoEJtg4ojdEAB7RxFqQk3nAAxALGXqMj21A/2LhLrJxZYAxAoz1NpsvYxnpm1Qnvz8z oBKadGhJ7/uvXccTTjIs6aT/og9tMPY= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=TrfD3g9L; spf=pass (imf15.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712054607; h=from:from: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:autocrypt:autocrypt; bh=/zBpNACLXUrqP92by+X1aP2sLL3r5R2IUOWqrDEJp1g=; b=TrfD3g9L0L72VE/QsXd3+VZHpyIy5nO8YLBXE5PENNTuZ+ccE2QJX4QhRebY+kr6rzckuy PisAut3LhPOhkno/WzUDrobYb5Xp6h6ukrXb+y37ZN6buEkLHA4RNZwXB/vscyYi+viSQm nlwaAkiafIiqpKHYzhp7VC5Kl7/yq5Q= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-316-37IMV7FNPAOIklYBwK1i5A-1; Tue, 02 Apr 2024 06:43:24 -0400 X-MC-Unique: 37IMV7FNPAOIklYBwK1i5A-1 Received: by mail-wr1-f70.google.com with SMTP id ffacd0b85a97d-34364bba472so290296f8f.1 for ; Tue, 02 Apr 2024 03:43:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712054603; x=1712659403; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=/zBpNACLXUrqP92by+X1aP2sLL3r5R2IUOWqrDEJp1g=; b=iU/bOHNPGLWckoABCfFEpHC/q3ShaLwv0dTOQHHPHNd+ZS5o0N1WfcaOaSUw5qn3BA Baw11dhbgzuDjN8AljyTblnVWsip0vxrIz0NrDAHUnlALuQqbBP2yMJiAY/n1Ovuu8HF o1PrTp5kP+MAuksvWp1SWYoDXkkEveMztLRE5O4KoSCuE8ysjmgqOmpR7su/WDWgU4Y7 Lvqg7QCqduI/kuglphic7L4QZ00upbTSIJ0VWjIiT62vdagrxYHmW3syE82vArCawNoq XjXHTa+Bb747oJDS5KCS3bzd6m2sGWznnXvWfILr9ySO54TD98HnnPqg75Xwj4L3lssX Zs/Q== X-Forwarded-Encrypted: i=1; AJvYcCWWegr+dCHpJtr8rmWO5+MwtHctjQHKEtwz0WNU25ONspZhJWA14rIH3Dlv65pGKEqwqP9onrL/O8bFXyPIsK7hZtk= X-Gm-Message-State: AOJu0YxT43EIgPrNGHZ3OwwXIHfkaEc/AYlY8wtVtdS5J45aPUn4b8v0 xmIKlQ8JVL1gIQCwVrJV+JliXUrtOofns9/fC3Rd1l9luG39Eapd+2ORZYMm+/SSa0yMLSgLLxo ifos/E1ESIzeX4HMREzCrd9hRCAx/FjO7kFc8ASYu6JpMLw8C X-Received: by 2002:a05:6000:a88:b0:341:bff9:2e4f with SMTP id dh8-20020a0560000a8800b00341bff92e4fmr8755270wrb.44.1712054603369; Tue, 02 Apr 2024 03:43:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEMjSHZUX7iIjKevMw2JKGtsNyP/yuvCusbIVuPhi0qT6T+AUonf5RaUivG/+/DpAKEAfumkg== X-Received: by 2002:a05:6000:a88:b0:341:bff9:2e4f with SMTP id dh8-20020a0560000a8800b00341bff92e4fmr8755250wrb.44.1712054602910; Tue, 02 Apr 2024 03:43:22 -0700 (PDT) Received: from ?IPV6:2003:cb:c732:e600:4982:2903:710f:f20a? (p200300cbc732e60049822903710ff20a.dip0.t-ipconnect.de. [2003:cb:c732:e600:4982:2903:710f:f20a]) by smtp.gmail.com with ESMTPSA id a9-20020a056000050900b00341d7596ec0sm13783274wrf.15.2024.04.02.03.43.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Apr 2024 03:43:22 -0700 (PDT) Message-ID: <8118eabf-de9c-41a7-9892-3a1a5bd2071c@redhat.com> Date: Tue, 2 Apr 2024 12:43:21 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: init_mlocked_on_free_v3 To: York Jasper Niebuhr , akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org References: <20240329145605.149917-1-yjnworkstation@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <20240329145605.149917-1-yjnworkstation@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: hew46eanm74io3b18zgsap8g466k5nqq X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8F095A0012 X-Rspam-User: X-HE-Tag: 1712054608-999369 X-HE-Meta: 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 lEynA9gR 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 29.03.24 15:56, York Jasper Niebuhr wrote: > Implements the "init_mlocked_on_free" boot option. When this boot option > is enabled, any mlock'ed pages are zeroed on free. If > the pages are munlock'ed beforehand, no initialization takes place. > This boot option is meant to combat the performance hit of > "init_on_free" as reported in commit 6471384af2a6 ("mm: security: > introduce init_on_alloc=1 and init_on_free=1 boot options"). With > "init_mlocked_on_free=1" only relevant data is freed while everything > else is left untouched by the kernel. Correspondingly, this patch > introduces no performance hit for unmapping non-mlock'ed memory. The > unmapping overhead for purely mlocked memory was measured to be > approximately 13%. Realistically, most systems mlock only a fraction of > the total memory so the real-world system overhead should be close to > zero. > > Optimally, userspace programs clear any key material or other > confidential memory before exit and munlock the according memory > regions. If a program crashes, userspace key managers fail to do this > job. Accordingly, no munlock operations are performed so the data is > caught and zeroed by the kernel. Should the program not crash, all > memory will ideally be munlocked so no overhead is caused. > > CONFIG_INIT_MLOCKED_ON_FREE_DEFAULT_ON can be set to enable > "init_mlocked_on_free" by default. > > Signed-off-by: York Jasper Niebuhr I'm not convinced that this is the right approach. You seem to be focused on "don't leak secrets stored in user space somewhere else". Well, and assuming that no other users on such systems use mlock() for a different purpose where the additional clearing will just be overhead. In general, I'm not a fan of any such kernel cmdline options. Really, we want to handle memory that stores secrets always in a sane way. Note that in the meantime, we do have secretmem for that purpose, which primary use case -- in contrast to mlock -- is to store secrets. I now that "teach user space to use secretmem" is not a good answer, but further emphasizing "mlock means storing secrets" feels wrong. Also note that your patch won't handle all cases: mlocked folios can be migrated in memory. But there is no such code that handles freeing of the source page during migration, so you could still leak memory at least there ... (I was briefly thinking about a VMA option, independent of mlock, to achieve that. But likely just using secretmem might be the better long-term approach) -- Cheers, David / dhildenb