selftests: mm: check return values

Check return value and return error/skip the tests.

Link: https://lkml.kernel.org/r/20240520185248.1801945-1-usama.anjum@collabora.com
Fixes: 46fd75d4 ("selftests: mm: add pagemap ioctl tests")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/pagemap_ioctl.c

@@ -1567,8 +1567,10 @@ int main(int argc, char *argv[])
 	/* 7. File Hugetlb testing */
 	mem_size = 2*1024*1024;
 	fd = memfd_create("uffd-test", MFD_HUGETLB | MFD_NOEXEC_SEAL);
+	if (fd < 0)
+		ksft_exit_fail_msg("uffd-test creation failed %d %s\n", errno, strerror(errno));
 	mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-	if (mem) {
+	if (mem != MAP_FAILED) {
 		wp_init(mem, mem_size);
 		wp_addr_range(mem, mem_size);