[PATCH RFC 08/17] KVM: selftests: Test rejection of tmpfs file for resource_fd

[Ackerley Tng via B4 Relay]

From: Ackerley Tng <ackerleytng@xxxxxxxxxx>

Add test coverage verifying that passing a regular file from tmpfs
as a resource file fails with ENOTDIR. Only directory file descriptors
representing the mount root are supported as resource pools.

Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index 31bc74c4c26bd..a7a1b5470cb2c 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -457,6 +457,26 @@ static void test_resource_fd_unsupported_fs(struct kvm_vm *vm)
 	close(file_fd);
 }
 
+static void test_resource_fd_tmpfs_file(struct kvm_vm *vm)
+{
+	int fd, file_fd;
+
+	/*
+	 * Passing a regular file from tmpfs (e.g. via memfd) is rejected by
+	 * the provider attach callback with ENOTDIR because only directory
+	 * FDs representing the mount root are supported resource pools.
+	 */
+	file_fd = memfd_create("test_tmpfs_file", 0);
+	TEST_ASSERT(file_fd >= 0, "memfd_create 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 file fd should fail");
+	TEST_ASSERT_EQ(errno, ENOTDIR);
+	close(file_fd);
+}
+
 #define ____gmem_test(__test, __vm, __flags, __gmem_size, args...)	\
 do {									\
 	int fd = vm_create_guest_memfd(__vm, __gmem_size, __flags);	\
@@ -517,6 +537,7 @@ static void test_guest_memfd(unsigned long vm_type)
 
 	test_resource_fd_invalid(vm);
 	test_resource_fd_unsupported_fs(vm);
+	test_resource_fd_tmpfs_file(vm);
 
 	__test_guest_memfd(vm, 0);
 

-- 
2.56.0.rc1.315.gc6ed9934b7-goog