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([2a02:8084:e84:2480:228:f8ff:fe6f:83a8]) by smtp.gmail.com with ESMTPSA id h9sm13686374wmm.33.2021.06.11.11.37.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 11 Jun 2021 11:37:54 -0700 (PDT) Subject: Re: [PATCH v3 23/23] x86/vdso/selftest: Add a test for unmapping vDSO To: Shuah Khan , Dmitry Safonov , linux-kernel@vger.kernel.org Cc: Alexander Viro , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christophe Leroy , Guo Ren , "H. Peter Anvin" , Ingo Molnar , Oleg Nesterov , Russell King , Thomas Bogendoerfer , Thomas Gleixner , Vincenzo Frascino , Will Deacon , x86@kernel.org, Shuah Khan References: <20210611180242.711399-1-dima@arista.com> <20210611180242.711399-24-dima@arista.com> From: Dmitry Safonov <0x7f454c46@gmail.com> Message-ID: <696c19f6-8606-0981-dc74-a8541ebddcc0@gmail.com> Date: Fri, 11 Jun 2021 19:37:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/11/21 7:21 PM, Shuah Khan wrote: > On 6/11/21 12:02 PM, Dmitry Safonov wrote: >> Output for landing on x86: >>> [root@localhost ~]# ./test_munmap_vdso_64 >>>     AT_SYSINFO_EHDR is 0x7fffead9f000 >>> [NOTE]    unmapping vDSO: [0x7fffead9f000, 0x7fffeada0000] >>> [NOTE]    vDSO partial move failed, will try with bigger size >>> [NOTE]    unmapping vDSO: [0x7fffead9f000, 0x7fffeada1000] >>> [OK] >>> [root@localhost ~]# ./test_munmap_vdso_32 >>>     AT_SYSINFO_EHDR is 0xf7eef000 >>> [NOTE]    unmapping vDSO: [0xf7eef000, 0xf7ef0000] >>> [NOTE]    vDSO partial move failed, will try with bigger size >>> [NOTE]    unmapping vDSO: [0xf7eef000, 0xf7ef1000] >>> [OK] >> >> The test also can check force_sigsegv(SIGSEGV) in do_fast_syscall_32(): >>> [root@localhost ~]# ./test_munmap_vdso_32 sysenter >>> [NOTE]    Using sysenter after munmap >>>     AT_SYSINFO_EHDR is 0xf7efe000 >>> [NOTE]    unmapping vDSO: [0xf7efe000, 0xf7eff000] >>> [NOTE]    vDSO partial move failed, will try with bigger size >>> [NOTE]    unmapping vDSO: [0xf7efe000, 0xf7f00000] >>> [OK]    32-bit process gets segfault on fast syscall with unmapped vDSO >> >> Cc: Shuah Khan >> Signed-off-by: Dmitry Safonov >> --- >>   tools/testing/selftests/x86/.gitignore        |   1 + >>   tools/testing/selftests/x86/Makefile          |  11 +- >>   .../testing/selftests/x86/test_munmap_vdso.c  | 151 ++++++++++++++++++ >>   3 files changed, 158 insertions(+), 5 deletions(-) >>   create mode 100644 tools/testing/selftests/x86/test_munmap_vdso.c >> > > I can take this through kselftest tree for 5.14 - are there any > dependencies on x86 tree, I should be aware of? The test should work without other patches from the set. So I guess, it's good to go by it's own. The only note I can make here is that without previous patches this part of the commit message is not exactly precise: > The test also can check force_sigsegv(SIGSEGV) in > do_fast_syscall_32() I will still crash, but not by the kernel enforcement, rather with landing on the area where vdso was previously mapped. Thanks, Dmitry