s390/seccomp: add support for system call filtering using BPF

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index f4eb376..e4be113 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -719,7 +719,11 @@
 	long ret = 0;
 
 	/* Do the secure computing check first. */
-	secure_computing_strict(regs->gprs[2]);
+	if (secure_computing(regs->gprs[2])) {
+		/* seccomp failures shouldn't expose any additional code. */
+		ret = -1;
+		goto out;
+	}
 
 	/*
 	 * The sysc_tracesys code in entry.S stored the system
@@ -745,6 +749,7 @@
 			    regs->gprs[2], regs->orig_gpr2,
 			    regs->gprs[3], regs->gprs[4],
 			    regs->gprs[5]);
+out:
 	return ret ?: regs->gprs[2];
 }