linux-kernel - Re: [PATCH for-next/seccomp v2 1/2] selftests/seccomp: Add SKIPs for failed unshare()

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Date:   Sat, 11 Jul 2020 10:05:35 -0600
From:   Tycho Andersen <tycho@...ho.ws>
To:     Kees Cook <keescook@...omium.org>
Cc:     Will Deacon <will@...nel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Shuah Khan <shuah@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH for-next/seccomp v2 1/2] selftests/seccomp: Add SKIPs for
 failed unshare()

On Fri, Jul 10, 2020 at 04:01:06PM -0700, Kees Cook wrote:
> Running the seccomp tests as a regular user shouldn't just fail tests
> that require CAP_SYS_ADMIN (for getting a PID namespace). Instead,
> detect those cases and SKIP them. Additionally, gracefully SKIP missing
> CONFIG_USER_NS (and add to "config" since we'd prefer to actually test
> this case).
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  tools/testing/selftests/seccomp/config        |  1 +
>  tools/testing/selftests/seccomp/seccomp_bpf.c | 10 ++++++++--
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/seccomp/config b/tools/testing/selftests/seccomp/config
> index db1e11b08c8a..64c19d8eba79 100644
> --- a/tools/testing/selftests/seccomp/config
> +++ b/tools/testing/selftests/seccomp/config
> @@ -1,2 +1,3 @@
>  CONFIG_SECCOMP=y
>  CONFIG_SECCOMP_FILTER=y
> +CONFIG_USER_NS=y
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
> index c0aa46ce14f6..14b038361549 100644
> --- a/tools/testing/selftests/seccomp/seccomp_bpf.c
> +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
> @@ -3439,7 +3439,10 @@ TEST(user_notification_child_pid_ns)
>  	struct seccomp_notif req = {};
>  	struct seccomp_notif_resp resp = {};
>  
> -	ASSERT_EQ(unshare(CLONE_NEWUSER | CLONE_NEWPID), 0);
> +	ASSERT_EQ(unshare(CLONE_NEWUSER | CLONE_NEWPID), 0) {
> +		if (errno == EINVAL)
> +			SKIP(return, "kernel missing CLONE_NEWUSER support");
> +	};
>  
>  	listener = user_trap_syscall(__NR_getppid,
>  				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
> @@ -3504,7 +3507,10 @@ TEST(user_notification_sibling_pid_ns)
>  	}
>  
>  	/* Create the sibling ns, and sibling in it. */
> -	ASSERT_EQ(unshare(CLONE_NEWPID), 0);
> +	ASSERT_EQ(unshare(CLONE_NEWPID), 0) {
> +		if (errno == EPERM)
> +			SKIP(return, "CLONE_NEWPID requires CAP_SYS_ADMIN");
> +	}
>  	ASSERT_EQ(errno, 0);

For this one, I think we can just put an unshare(CLONE_NEWUSER) at
the top so the test still runs. This seems works for me unprivileged:

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 252140a52553..65e3642539f9 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -3482,6 +3482,11 @@ TEST(user_notification_sibling_pid_ns)
 		TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!");
 	}
 
+	ASSERT_EQ(unshare(CLONE_NEWUSER), 0) {
+		if (errno == EINVAL)
+			SKIP(return, "kernel missing CLONE_NEWUSER support");
+	};
+
 	listener = user_trap_syscall(__NR_getppid,
 				     SECCOMP_FILTER_FLAG_NEW_LISTENER);
 	ASSERT_GE(listener, 0);