[LTP] [PATCH v2] syscalls/userfaultfd01: add hint about unprivileged_userfaultfd

[Yang Xu]

Hi Li
> 
> 
> On Wed, Dec 18, 2019 at 12:02 PM Yang Xu <xuyang2018.jy@cn.fujitsu.com 
> <mailto:xuyang2018.jy@cn.fujitsu.com>> wrote:
> 
>     Since commit cefdca0a86be ("userfaultfd/sysctl: add
>     vm.unprivileged_userfaultfd").
>     , it adds a global sysctl knob "vm.unprivileged_userfaultfd" to
>     control whether
>     unprivileged users can use the userfaultfd system calls. Set this to
>     1 to allow
>     unprivileged users to use the userfaultfd system calls, or set this
>     to 0 to
>     restrict userfaultfd to only privileged users (with SYS_CAP_PTRACE
>     capability). The
>     default value is 1. Add hint about it.
> 
> 
> Can we do the "vm.unprivileged_userfaultfd" check in the setup() and do 
> set to 1 if it exists?
I remembered Jan Stancek has a patch about bpf hint about 
unprivileged_bpf_disabled, I do as same as that patch did.

Also, month agos about acct02 discussion, Cyril points about adjusting
the threshold value of resume and suppend to make case passes.

So, I have a question that we have unified standards about these cases
(bpf, acct02, affected by sysctl)? Report TCONF or modify argument to
make case passes?

@Cyril and @Jan Stancek What do you think about it?

> And maybe we need more tests for the global sysctl knob 
> "vm.unprivileged_userfaultfd".Eeven though we don't have case to test unprivileged_bpf_disabled. I 
still think testing unprivileged_userfaultfd is meaningful and we can 
begin with it.

Best Regards
Yang Xu
> 
> 
>     Signed-off-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com
>     <mailto:xuyang2018.jy@cn.fujitsu.com>>
>     ---
>       .../syscalls/userfaultfd/userfaultfd01.c      | 19 +++++++++++++------
>       1 file changed, 13 insertions(+), 6 deletions(-)
> 
>     diff --git a/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
>     b/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
>     index a5e142209..4e178b4f8 100644
>     --- a/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
>     +++ b/testcases/kernel/syscalls/userfaultfd/userfaultfd01.c
>     @@ -82,12 +82,19 @@ static void run(void)
> 
>              set_pages();
> 
>     -       uffd = sys_userfaultfd(O_CLOEXEC | O_NONBLOCK);
>     -
>     -       if (uffd == -1)
>     -               tst_brk(TBROK | TERRNO,
>     -                       "Could not create userfault file descriptor");
>     -
>     +       TEST(sys_userfaultfd(O_CLOEXEC | O_NONBLOCK));
>     +
>     +       if (TST_RET == -1) {
>     +               if (TST_ERR == EPERM) {
>     +                       tst_res(TCONF, "Hint: check
>     /proc/sys/vm/unprivileged_userfaultfd");
>     +                       tst_brk(TCONF | TTERRNO,
>     +                               "userfaultfd() requires
>     CAP_SYS_PTRACE on this system");
>     +               } else
>     +                       tst_brk(TBROK | TTERRNO,
>     +                               "Could not create userfault file
>     descriptor");
>     +       }
>     +
>     +       uffd = TST_RET;
>              uffdio_api.api = UFFD_API;
>              uffdio_api.features = 0;
>              SAFE_IOCTL(uffd, UFFDIO_API, &uffdio_api);
>     -- 
>     2.18.0
> 
> 
> 
> 
>     -- 
>     Mailing list info: https://lists.linux.it/listinfo/ltp
> 
> 
> 
> -- 
> Regards,
> Li Wang