selftest/futex: Reintroduce "Memory out of range" numa_mpol's subtest

JIRA: https://issues.redhat.com/browse/RHEL-101190

commit 2951ddd
Author: André Almeida <andrealmeid@igalia.com>
Date:   Mon, 15 Sep 2025 23:26:29 +0200

    selftest/futex: Reintroduce "Memory out of range" numa_mpol's subtest

    Commit d8e2f91 ("selftests/futex: Fix some futex_numa_mpol
    subtests") removed the "Memory out of range" subtest due to it being
    dependent on the memory layout of the test process having an invalid
    memory address just after the `*futex_ptr` allocated memory.

    Reintroduce this test and make it deterministic, by allocation two
    memory pages and marking the second one with PROT_NONE.

    Signed-off-by: André Almeida <andrealmeid@igalia.com>
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Reviewed-by: Waiman Long <longman@redhat.com>

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

tools/testing/selftests/futex/functional/futex_numa_mpol.c

@@ -174,10 +174,13 @@ int main(int argc, char *argv[])
 	ksft_set_plan(1);
 
 	mem_size = sysconf(_SC_PAGE_SIZE);
-	futex_ptr = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+	futex_ptr = mmap(NULL, mem_size * 2, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
 	if (futex_ptr == MAP_FAILED)
 		ksft_exit_fail_msg("mmap() for %d bytes failed\n", mem_size);
 
+	/* Create an invalid memory region for the "Memory out of range" test */
+	mprotect(futex_ptr + mem_size, mem_size, PROT_NONE);
+
 	futex_numa = futex_ptr;
 
 	ksft_print_msg("Regular test\n");
@@ -192,6 +195,9 @@ int main(int argc, char *argv[])
 	ksft_print_msg("Mis-aligned futex\n");
 	test_futex(futex_ptr + mem_size - 4, EINVAL);
 
+	ksft_print_msg("Memory out of range\n");
+	test_futex(futex_ptr + mem_size, EFAULT);
+
 	futex_numa->numa = FUTEX_NO_NODE;
 	mprotect(futex_ptr, mem_size, PROT_READ);
 	ksft_print_msg("Memory, RO\n");