Re: [PATCH v2] linux: return UNSUPPORTED in tst-mount if !support_can_chroot

[Florian Weimer <fweimer@redhat.com>]

* Michael Hudson-Doyle via Libc-alpha:

> Otherwise the test fails if run in a chroot by a non-root user:
>
> 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
> ---
> v2: check support_can_chroot() rather than support_become_root return
> value
> ---
>  sysdeps/unix/sysv/linux/tst-mount.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/sysdeps/unix/sysv/linux/tst-mount.c b/sysdeps/unix/sysv/linux/tst-mount.c
> index 502d7e3433..a0b367d9df 100644
> --- a/sysdeps/unix/sysv/linux/tst-mount.c
> +++ b/sysdeps/unix/sysv/linux/tst-mount.c
> @@ -20,6 +20,7 @@
>  #include <support/check.h>
>  #include <support/xunistd.h>
>  #include <support/namespace.h>
> +#include <support/test-driver.h>
>  #include <sys/wait.h>
>  #include <sys/mount.h>
>  
> @@ -104,6 +105,8 @@ static int
>  do_test (void)
>  {
>    support_become_root ();
> +  if (!support_can_chroot ())
> +    return EXIT_UNSUPPORTED;
>  
>    pid_t pid = xfork ();
>    if (pid == 0)

This test still hoses the system if run as root on a system without user
namespaces.

I think you should call and check support_enter_mount_namespace instead,
to make sure that the test does not modify the original mount namespace.

Thanks,
Florian