[PATCH v3] linux: return UNSUPPORTED from tst-mount if entering mount namespace fails

[Carlos O'Donell]

On 7/17/22 19:16, Michael Hudson-Doyle via Libc-alpha wrote:
> Before this the test fails if run in a chroot by a non-root user:

LGTM. OK for glibc 2.36. Would you like me to push this for you?

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
 
> warning: could not become root outside namespace (Operation not permitted)
> ../sysdeps/unix/sysv/linux/tst-mount.c:36: numeric comparison failure
>    left: 1 (0x1); from: errno
>   right: 19 (0x13); from: ENODEV
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:39: not true: fd != -1
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:46: not true: r != -1
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:48: not true: r != -1
> ../sysdeps/unix/sysv/linux/tst-mount.c:52: numeric comparison failure
>    left: 1 (0x1); from: errno
>   right: 9 (0x9); from: EBADF
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:55: not true: mfd != -1
> ../sysdeps/unix/sysv/linux/tst-mount.c:58: numeric comparison failure
>    left: 1 (0x1); from: errno
>   right: 2 (0x2); from: ENOENT
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:61: not true: r != -1
> ../sysdeps/unix/sysv/linux/tst-mount.c:65: numeric comparison failure
>    left: 1 (0x1); from: errno
>   right: 2 (0x2); from: ENOENT
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:68: not true: pfd != -1
> error: ../sysdeps/unix/sysv/linux/tst-mount.c:75: not true: fd_tree != -1
> ../sysdeps/unix/sysv/linux/tst-mount.c:88: numeric comparison failure
>    left: 1 (0x1); from: errno
>   right: 38 (0x26); from: ENOSYS
> error: 12 test failures
> 
> Checking that the test can enter a new mount namespace is more correct
> than just checking the return value of support_become_root() as the test
> code changes the mount namespace it runs in so running it as root on a
> system that does not support mount namespaces should still skip.

Agreed.

> 
> Also change the test to remove the unnecessary fork.
> ---
> v3: check support_enter_mount_namespace() return value, remove fork
> v2: check support_can_chroot() rather than support_become_root return
> value
> ---
>  sysdeps/unix/sysv/linux/tst-mount.c | 25 ++++++-------------------
>  1 file changed, 6 insertions(+), 19 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/tst-mount.c b/sysdeps/unix/sysv/linux/tst-mount.c
> index 502d7e3433..b6333a60e6 100644
> --- a/sysdeps/unix/sysv/linux/tst-mount.c
> +++ b/sysdeps/unix/sysv/linux/tst-mount.c
> @@ -20,15 +20,18 @@
>  #include <support/check.h>
>  #include <support/xunistd.h>
>  #include <support/namespace.h>
> -#include <sys/wait.h>

OK.

>  #include <sys/mount.h>
>  
>  _Static_assert (sizeof (struct mount_attr) == MOUNT_ATTR_SIZE_VER0,
>  		"sizeof (struct mount_attr) != MOUNT_ATTR_SIZE_VER0");
>  
> -static void
> -subprocess (void)
> +static int
> +do_test (void)

OK.

>  {
> +  support_become_root ();
> +  if (!support_enter_mount_namespace ())
> +    FAIL_UNSUPPORTED ("cannot enter mount namespace, skipping test");

OK.

> +
>    int r = fsopen ("it_should_be_not_a_valid_mount", 0);
>    TEST_VERIFY_EXIT (r == -1);
>    if (errno == ENOSYS)
> @@ -100,20 +103,4 @@ subprocess (void)
>    _exit (0);
>  }
>  
> -static int
> -do_test (void)
> -{
> -  support_become_root ();
> -
> -  pid_t pid = xfork ();
> -  if (pid == 0)
> -    subprocess ();
> -
> -  int status;
> -  xwaitpid (pid, &status, 0);
> -  TEST_VERIFY (WIFEXITED (status));
> -
> -  return 0;
> -}
> -
>  #include <support/test-driver.c>


-- 
Cheers,
Carlos.