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

[Shuah Khan]

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@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 <shuah@xxxxxxxxxx>
> > > Signed-off-by: Dmitry Safonov <dima@xxxxxxxxxx>
> > > ---
> > >    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@xxxxxxxxxxxxxxxxxxx>

thanks,
-- Shuah