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[87.161.167.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a35ca8894csm11768115f8f.76.2025.05.19.00.43.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 May 2025 00:43:06 -0700 (PDT) Message-ID: <95f07257-1ca6-4104-8389-fa8ce97bd239@redhat.com> Date: Mon, 19 May 2025 09:43:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Question: a module for wiping userspace RAM before shutdown/reboot/halt To: Danill Klimuk , Christophe Leroy , linux-modules@vger.kernel.org, "linux-mm@kvack.org" References: 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: f8HobuiExRZQwF8CfpzTX6KPYE_xM0Jx7zsAJdh4mGk_1747640587 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 47EA0A0006 X-Stat-Signature: bg9z37idrnrry17m9qs5wan9awngr3yb X-Rspam-User: X-HE-Tag: 1747640591-43888 X-HE-Meta: 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 etc+I/3F qQbJR26xFKtx33Sfs78Jsk5R1db6v8qvmCv76nbukB0pAdYTIW7VNwhk6vkdn2WQ0F8tYdxUj7kzpZlzptiqdw/v6TCIq1zHhiNOqnVkTptnFbsjH4DR+DkWOe5XfUkiVzWwwanxzWq/QTMnpwN+Om9Pw5tqSi8wygDfPh0hTb74AVtZ/ogXCg4zLYsEq2bTvouaexGfifXrDGj2qVbFMm/SJNyPkLjVH8WbmeQTgxAHzLA6HY1zWCUP8KFsu+dL38oxG+xRuBe5qWGqd7OYUXAirr0JWNSSPXE/L2rMwsxw00TLRlVGJpNNDwJeXcGZsUf+/C6rcKg/E4gGUfbut9wDZybKgMNeN9rsNxaqA2Hrk4ecGOzo0tzwj6m+pa6WbCzk5AOLVLmcmaBEBA6i9NgYxOe1vxBl7llXxgY5oKJDn4jt/keVwcQxxs7vVXgEEDjRyDLEap4CEfbM= 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 19.05.25 09:26, Danill Klimuk wrote: > Hi Christophe, thank you for the answer. > > > What do you mean by 'wiping', do you mean 'clearing' ? > > Yes, by 'wiping' I mean 'clearing'. > > > Can you explain the reason this is needed? > > Some of our clients want to clear user space RAM during > shutdown/reboot/halt sequences of Linux kernel, so the process data or > any other leftovers do not leak outside current Linux kernel session > (that is to firmware, or the next boot software, etc.). The reason for > it to be a module that will execute in a specific moment of the > sequences is to make it more predictable. > > I thought that if the clients want to use it, maybe it will be useful > for others too :). We do have the init_on_free=1 boot option, whereby any pages freed back to the page allocator will get immediately zeroed. This also makes sure that if you quit a process and then shutdown/reboot, that the page content was already cleared. (otherwise, it would simply be free memory in the allocator and no longer "userspace RAM") -- Cheers, David / dhildenb