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[2003:cb:c74f:2500:1e3a:9ee0:5180:cc13]) by smtp.gmail.com with ESMTPSA id o2-20020a1c7502000000b003f195d540d9sm2256533wmc.14.2023.05.16.05.55.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 May 2023 05:55:02 -0700 (PDT) Message-ID: <72fc50da-c3b9-b71b-209b-9413a8693f13@redhat.com> Date: Tue, 16 May 2023 14:55:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v2 3/4] mm: page_table_check: Make it dependent on EXCLUSIVE_SYSTEM_RAM To: Ruihan Li , linux-mm@kvack.org, linux-usb@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Pasha Tatashin , Matthew Wilcox , Andrew Morton , Christoph Hellwig , Alan Stern , Greg Kroah-Hartman , stable@vger.kernel.org References: <20230515130958.32471-1-lrh2000@pku.edu.cn> <20230515130958.32471-4-lrh2000@pku.edu.cn> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230515130958.32471-4-lrh2000@pku.edu.cn> 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: wcznzhomgthuxqy3qd6sea8ro46o9ufy X-Rspam-User: X-Rspamd-Queue-Id: CEB63120009 X-Rspamd-Server: rspam07 X-HE-Tag: 1684241706-904427 X-HE-Meta: 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 obQi5SYs 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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: On 15.05.23 15:09, Ruihan Li wrote: > Without EXCLUSIVE_SYSTEM_RAM, users are allowed to map arbitrary > physical memory regions into the userspace via /dev/mem. At the same > time, pages may change their properties (e.g., from anonymous pages to > named pages) while they are still being mapped in the userspace, leading > to "corruption" detected by the page table check. > > To avoid these false positives, this patch makes PAGE_TABLE_CHECK > depends on EXCLUSIVE_SYSTEM_RAM. This dependency is understandable > because PAGE_TABLE_CHECK is a hardening technique but /dev/mem without > STRICT_DEVMEM (i.e., !EXCLUSIVE_SYSTEM_RAM) is itself a security > problem. > > Even with EXCLUSIVE_SYSTEM_RAM, I/O pages may be still allowed to be > mapped via /dev/mem. However, these pages are always considered as named > pages, so they won't break the logic used in the page table check. > > Cc: # 5.17 > Signed-off-by: Ruihan Li Acked-by: David Hildenbrand -- Thanks, David / dhildenb