[PATCH RFC v3 10/88] KVM: selftests: Test rejection of swap tmpfs mounts

[Ackerley Tng via B4 Relay <devnull+ackerleytng.google.com@kernel.org>]

From: Ackerley Tng <ackerleytng@google.com>

Test that guest_memfd creation fails with -EINVAL when passed a resource
pool fd for a mount that has swap enabled.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/guest_memfd_test.c | 70 ++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index d62ae23256083..205f822e10c6c 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -13,7 +13,9 @@
 
 #include <linux/bitmap.h>
 #include <linux/falloc.h>
+#include <linux/mount.h>
 #include <linux/sizes.h>
+#include <sys/mount.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 
@@ -478,6 +480,73 @@ static void test_resource_fd_memfd(struct kvm_vm *vm)
 	close(file_fd);
 }
 
+static int create_tmpfs_pool_fd(const char *huge, bool noswap, size_t size)
+{
+	char size_str[32];
+	char template[] = "/tmp/gmem_test_dir_XXXXXX";
+	char *mount_dir;
+	int fs_fd, mnt_fd, dir_fd;
+
+	TEST_ASSERT(size && IS_ALIGNED(size, page_size),
+		    "Pool size '0x%zx' must be positive and page-aligned", size);
+
+	fs_fd = syscall(__NR_fsopen, "tmpfs", FSOPEN_CLOEXEC);
+	TEST_ASSERT(fs_fd >= 0, "fsopen failed");
+
+	if (noswap)
+		TEST_ASSERT(!syscall(__NR_fsconfig, fs_fd, FSCONFIG_SET_FLAG,
+				     "noswap", NULL, 0), "fsconfig noswap failed");
+
+	if (huge)
+		TEST_ASSERT(!syscall(__NR_fsconfig, fs_fd, FSCONFIG_SET_STRING,
+				     "huge", huge, 0), "fsconfig huge failed");
+
+	snprintf(size_str, sizeof(size_str), "%zu", size);
+	TEST_ASSERT(!syscall(__NR_fsconfig, fs_fd, FSCONFIG_SET_STRING,
+			     "size", size_str, 0), "fsconfig size failed");
+
+	TEST_ASSERT(!syscall(__NR_fsconfig, fs_fd, FSCONFIG_CMD_CREATE,
+			     NULL, NULL, 0), "fsconfig create failed");
+
+	mnt_fd = syscall(__NR_fsmount, fs_fd, FSMOUNT_CLOEXEC, 0);
+	TEST_ASSERT(mnt_fd > 0, "fsmount failed");
+	close(fs_fd);
+
+	mount_dir = mkdtemp(template);
+	TEST_ASSERT(mount_dir, "mkdtemp failed");
+
+	TEST_ASSERT(!syscall(__NR_move_mount, mnt_fd, "", AT_FDCWD, mount_dir,
+			     MOVE_MOUNT_F_EMPTY_PATH), "move_mount failed");
+	close(mnt_fd);
+
+	dir_fd = open(mount_dir, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
+	TEST_ASSERT(dir_fd >= 0, "open tmpfs mount directory failed");
+
+	/*
+	 * Detach mount from namespace so removing mount_dir upon exit or
+	 * unmount doesn't conflict, while dir_fd retains the active mount.
+	 */
+	TEST_ASSERT(!umount2(mount_dir, MNT_DETACH), "umount2 failed");
+	TEST_ASSERT(!rmdir(mount_dir), "rmdir failed");
+
+	return dir_fd;
+}
+
+static void test_resource_fd_tmpfs_swap(struct kvm_vm *vm)
+{
+	int pool_fd, fd;
+
+	pool_fd = create_tmpfs_pool_fd("never", false, page_size);
+
+	fd = __vm_create_guest_memfd_resource(vm, page_size,
+					      GUEST_MEMFD_FLAG_USE_RESOURCE,
+					      pool_fd);
+	TEST_ASSERT(fd < 0, "guest_memfd with swap-enabled tmpfs should fail");
+	TEST_ASSERT_EQ(errno, EINVAL);
+
+	close(pool_fd);
+}
+
 #define ____gmem_test(__test, __vm, __flags, __gmem_size, args...)	\
 do {									\
 	int fd = vm_create_guest_memfd(__vm, __gmem_size, __flags);	\
@@ -539,6 +608,7 @@ static void test_guest_memfd(unsigned long vm_type)
 	test_resource_fd_invalid(vm);
 	test_resource_fd_unsupported_fs(vm);
 	test_resource_fd_memfd(vm);
+	test_resource_fd_tmpfs_swap(vm);
 
 	__test_guest_memfd(vm, 0);
 

-- 
2.56.0.455.g6c5a503b38-goog