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[2003:cb:c738:3100:8133:26cf:7877:94aa]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436e9d8fc5csm171535915e9.2.2025.01.14.02.15.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Jan 2025 02:15:35 -0800 (PST) Message-ID: Date: Tue, 14 Jan 2025 11:15:28 +0100 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 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 Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kernel test robot References: <20250113-virtual_address_range-tests-v3-0-f4a8e6b7feed@linutronix.de> <20250113-virtual_address_range-tests-v3-4-f4a8e6b7feed@linutronix.de> From: David Hildenbrand Content-Language: en-US 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: <20250113-virtual_address_range-tests-v3-4-f4a8e6b7feed@linutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 13.01.25 14:15, 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 > > Revert "selftests/mm: virtual_address_range: Avoid reading VVAR mappings" > > This reverts commit 05cc5d292ac4238684b59922aecf59c932edefa0. > --- > tools/testing/selftests/mm/virtual_address_range.c | 4 ++++ > tools/testing/selftests/mm/vm_util.c | 21 +++++++++++++++++++++ > tools/testing/selftests/mm/vm_util.h | 1 + > 3 files changed, 26 insertions(+) > > diff --git a/tools/testing/selftests/mm/virtual_address_range.c b/tools/testing/selftests/mm/virtual_address_range.c > index 386e4e46fa65b98af78dee4bb30144eb2b51f528..b380e102b22f0a44654ab046f257e8c35e8d90e9 100644 > --- a/tools/testing/selftests/mm/virtual_address_range.c > +++ b/tools/testing/selftests/mm/virtual_address_range.c > @@ -15,6 +15,7 @@ > #include > #include > > +#include "vm_util.h" > #include "../kselftest.h" > > /* > @@ -159,6 +160,9 @@ static int validate_complete_va_space(void) > if (prot[0] != 'r') > continue; > > + if (check_vmflag_io((void *)start_addr)) > + continue; > + > /* > * Confirm whether MAP_CHUNK_SIZE chunk can be found or not. > * If write succeeds, no need to check MAP_CHUNK_SIZE - 1 > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index 8468a19d6acca10c7e9228c03a935cdeb2402b5d..161fe03b07af78244efc669a36155ad603fa6f7d 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -400,3 +400,24 @@ unsigned long get_free_hugepages(void) > fclose(f); > return fhp; > } > + > +bool check_vmflag_io(void *addr) Interestingly, this will only work if addr really is the start of the mapping, as __get_smap_entry() cannot handle "address falls into a mapping". Good enough for now, but might be worth a comment. (wrong usage would fail with No VmFlags for ... ) > +{ > + char *saveptr, *flag, *strtok_arg; " On some implementations, *saveptr is required to be NULL on the first call to strtok_r() that is being used to parse str." Maybe just initialize it to NULL. > + char buffer[MAX_LINE_LENGTH]; > + > + strtok_arg = __get_smap_entry(addr, "VmFlags:", buffer, sizeof(buffer)); > + if (!strtok_arg) > + ksft_exit_fail_msg("%s: No VmFlags for %p\n", __func__, addr); > + > + while (true) { > + flag = strtok_r(strtok_arg, " ", &saveptr); > + if (!flag) > + break; > + if (strcmp(flag, "io") == 0) > + return true; Are these early exit allowed with strtok_r()? An alternative seems to be using strcspn() that doesn't modify strings/maintain state in-between calls. -- Cheers, David / dhildenb