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[2003:cb:c708:e100:4f41:ff29:a59f:8c7a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436dcc8ddddsm79915705e9.0.2025.01.10.07.41.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jan 2025 07:41:04 -0800 (PST) Message-ID: <9243dd8e-3f03-4ed5-bdcf-95c947c57849@redhat.com> Date: Fri, 10 Jan 2025 16:41:03 +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 v2 3/3] selftests/mm: virtual_address_range: Avoid reading VVAR 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: <20250110-virtual_address_range-tests-v2-0-262a2bf3c3d0@linutronix.de> <20250110-virtual_address_range-tests-v2-3-262a2bf3c3d0@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 10.01.25 14:05, 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. > > Skip the various vvar mappings in virtual_address_range to avoid the issue. > > Fixes: e93d2521b27f ("x86/vdso: Split virtual clock pages into dedicated mapping") > Fixes: 010409649885 ("selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()") > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202412271148.2656e485-lkp@intel.com > Signed-off-by: Thomas Weißschuh > --- > tools/testing/selftests/mm/virtual_address_range.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/tools/testing/selftests/mm/virtual_address_range.c b/tools/testing/selftests/mm/virtual_address_range.c > index 4fc1c21a5e218eaec4d059b75c31a21dd4e8a215..993990aba56fc986c42084ffa91973558aa07e87 100644 > --- a/tools/testing/selftests/mm/virtual_address_range.c > +++ b/tools/testing/selftests/mm/virtual_address_range.c > @@ -152,6 +152,10 @@ static int validate_complete_va_space(void) > if (prot[0] != 'r') > continue; > > + /* Only the VDSO can know if a VVAR mapping is really readable */ > + if (vma_name && !strncmp(vma_name, "[vvar", 5)) > + continue; I'm wondering if there is a more generic way ... but likely not when staring at /proc/self/maps. /proc/self/smaps would indicate this as VM_IO: "io" VM_DONTDUMP: "dd" VM_PFNMAP: "pf" Especially checking for VM_IO sounds reasonable ... -- Cheers, David / dhildenb