[PATCH RFC v2 12/50] KVM: selftests: Test rejection of regular file in tmpfs mount

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@xxxxxxxxxx>

Add test coverage verifying that creating a regular file inside an
actual tmpfs mount and passing that file descriptor as resource_fd
fails with EOPNOTSUPP, because tmpfs regular files do not have
gmem_provider_ops defined on their file_operations.

Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 541d8cdd0bbf7..bef1acead4a6d 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -613,6 +613,25 @@ static void __test_guest_memfd(struct kvm_vm *vm, u64 flags)
 	gmem_test_vm(invalid_binding, vm, flags);
 }
 
+static void test_resource_fd_tmpfs_regular_file(struct kvm_vm *vm)
+{
+	int pool_fd, file_fd, fd;
+
+	pool_fd = create_tmpfs_pool_fd("never", true, page_size);
+
+	file_fd = openat(pool_fd, "regular_file", O_CREAT | O_RDWR | O_CLOEXEC, 0644);
+	TEST_ASSERT(file_fd >= 0, "openat regular_file in tmpfs pool failed");
+
+	fd = __vm_create_guest_memfd_resource(vm, page_size,
+					      GUEST_MEMFD_FLAG_USE_RESOURCE,
+					      file_fd);
+	TEST_ASSERT(fd < 0, "guest_memfd with tmpfs regular file should fail");
+	TEST_ASSERT_EQ(errno, EOPNOTSUPP);
+
+	close(file_fd);
+	close(pool_fd);
+}
+
 static void test_guest_memfd(unsigned long vm_type)
 {
 	struct kvm_vm *vm = vm_create_barebones_type(vm_type);
@@ -625,6 +644,7 @@ static void test_guest_memfd(unsigned long vm_type)
 	test_resource_fd_memfd(vm);
 	test_resource_fd_tmpfs_swap(vm);
 	test_resource_fd_tmpfs_huge(vm);
+	test_resource_fd_tmpfs_regular_file(vm);
 
 	__test_guest_memfd(vm, 0);
 

-- 
2.56.0.257.gf7497c7d27-goog