diff --git a/kernel/signal.c b/kernel/signal.c
index ccf1ceedaebef64b137553e2e82250dbfe6a7707..f268372c0cc06a54430ea3a4e4dbe8fbf39e2fb7 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2454,11 +2454,9 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 	stack_t oss;
 	int error;
 
-	if (uoss) {
-		oss.ss_sp = (void __user *) current->sas_ss_sp;
-		oss.ss_size = current->sas_ss_size;
-		oss.ss_flags = sas_ss_flags(sp);
-	}
+	oss.ss_sp = (void __user *) current->sas_ss_sp;
+	oss.ss_size = current->sas_ss_size;
+	oss.ss_flags = sas_ss_flags(sp);
 
 	if (uss) {
 		void __user *ss_sp;
@@ -2501,13 +2499,16 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 		current->sas_ss_size = ss_size;
 	}
 
+	error = 0;
 	if (uoss) {
 		error = -EFAULT;
-		if (copy_to_user(uoss, &oss, sizeof(oss)))
+		if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss)))
 			goto out;
+		error = __put_user(oss.ss_sp, &uoss->ss_sp) |
+			__put_user(oss.ss_size, &uoss->ss_size) |
+			__put_user(oss.ss_flags, &uoss->ss_flags);
 	}
 
-	error = 0;
 out:
 	return error;
 }