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[2003:cb:c738:3100:8133:26cf:7877:94aa]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436e9d26a7bsm187883795e9.0.2025.01.14.08.53.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Jan 2025 08:54:00 -0800 (PST) Message-ID: <56a1657c-d60f-4cdc-88a7-826ad977890f@redhat.com> Date: Tue, 14 Jan 2025 17:53:58 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/4] selftests/mm: virtual_address_range: Avoid reading from VM_IO mappings To: =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , Andrew Morton , Shuah Khan , Dev Jain , Thomas Gleixner , Anshuman Khandual Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot References: <20250114-virtual_address_range-tests-v4-0-6fd7269934a5@linutronix.de> <20250114-virtual_address_range-tests-v4-4-6fd7269934a5@linutronix.de> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 14.01.25 17:06, Thomas Weißschuh wrote: > The virtual_address_range selftest reads from the start of each mapping > listed in /proc/self/maps. > However not all mappings are valid to be arbitrarily accessed. > > For example the vvar data used for virtual clocks on x86 [vvar_vclock] > can only be accessed if 1) the kernel configuration enables virtual > clocks and 2) the hypervisor provided the data for it. > Only the VDSO itself has the necessary information to know this. > Since commit e93d2521b27f ("x86/vdso: Split virtual clock pages into dedicated mapping") > the virtual clock data was split out into its own mapping, leading > to EFAULT from read() during the validation. > > Check for the VM_IO flag as a proxy. > It is present for the VVAR mappings and MMIO ranges can be dangerous to > access arbitrarily. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202412271148.2656e485-lkp@intel.com > Fixes: e93d2521b27f ("x86/vdso: Split virtual clock pages into dedicated mapping") > Fixes: 010409649885 ("selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()") > Suggested-by: David Hildenbrand > Link: https://lore.kernel.org/lkml/e97c2a5d-c815-4936-a767-ac42a3220a90@redhat.com/ > Signed-off-by: Thomas Weißschuh Acked-by: David Hildenbrand Unfortunately, vsyscall doesn't seem to set VM_IO, it only has VmFlags: ex Which is rather weird. So we cannot remove that special-casing right now, -- Cheers, David / dhildenb