linux-kernel - Re: [PATCH v3 23/23] x86/vdso/selftest: Add a test for unmapping vDSO

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Message-ID: <dec726a9-25d5-491a-5ff1-72fe81a7f88f@linuxfoundation.org>
Date:   Fri, 11 Jun 2021 12:43:52 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Dmitry Safonov <0x7f454c46@...il.com>,
        Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        Shuah Khan <shuah@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v3 23/23] x86/vdso/selftest: Add a test for unmapping vDSO

On 6/11/21 12:37 PM, Dmitry Safonov wrote:
> 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@...alhost ~]# ./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@...alhost ~]# ./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@...alhost ~]# ./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 <shuah@...nel.org>
>>> Signed-off-by: Dmitry Safonov <dima@...sta.com>
>>> ---
>>>    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.
> 

Playing it safe, here is my Ack for it to go through x86 tree

Acked-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah