selftests/overlayfs: test specifying layers as O_PATH file descriptors

Verify that userspace can specify layers via O_PATH file descriptors.

Link: https://lore.kernel.org/r/20250210-work-overlayfs-v2-2-ed2a949b674b@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
index 1d0ae785a66779e6931e832d22ab20fb7ed6e951..e693e4102d22d929b42df82a3d7416b8b977b053 100644 (file)
--- a/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
+++ b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
@@ -214,4 +214,69 @@ TEST_F(set_layers_via_fds, set_500_layers_via_fds)
        ASSERT_EQ(close(fd_overlay), 0);
 }
 
+TEST_F(set_layers_via_fds, set_500_layers_via_opath_fds)
+{
+       int fd_context, fd_tmpfs, fd_overlay, fd_work, fd_upper, fd_lower;
+       int layer_fds[500] = { [0 ... 499] = -EBADF };
+
+       ASSERT_EQ(unshare(CLONE_NEWNS), 0);
+       ASSERT_EQ(sys_mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL), 0);
+
+       fd_context = sys_fsopen("tmpfs", 0);
+       ASSERT_GE(fd_context, 0);
+
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
+       fd_tmpfs = sys_fsmount(fd_context, 0, 0);
+       ASSERT_GE(fd_tmpfs, 0);
+       ASSERT_EQ(close(fd_context), 0);
+
+       for (int i = 0; i < ARRAY_SIZE(layer_fds); i++) {
+               char path[100];
+
+               sprintf(path, "l%d", i);
+               ASSERT_EQ(mkdirat(fd_tmpfs, path, 0755), 0);
+               layer_fds[i] = openat(fd_tmpfs, path, O_DIRECTORY | O_PATH);
+               ASSERT_GE(layer_fds[i], 0);
+       }
+
+       ASSERT_EQ(mkdirat(fd_tmpfs, "w", 0755), 0);
+       fd_work = openat(fd_tmpfs, "w", O_DIRECTORY | O_PATH);
+       ASSERT_GE(fd_work, 0);
+
+       ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
+       fd_upper = openat(fd_tmpfs, "u", O_DIRECTORY | O_PATH);
+       ASSERT_GE(fd_upper, 0);
+
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l501", 0755), 0);
+       fd_lower = openat(fd_tmpfs, "l501", O_DIRECTORY | O_PATH);
+       ASSERT_GE(fd_lower, 0);
+
+       ASSERT_EQ(sys_move_mount(fd_tmpfs, "", -EBADF, "/tmp", MOVE_MOUNT_F_EMPTY_PATH), 0);
+       ASSERT_EQ(close(fd_tmpfs), 0);
+
+       fd_context = sys_fsopen("overlay", 0);
+       ASSERT_GE(fd_context, 0);
+
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir",   NULL, fd_work), 0);
+       ASSERT_EQ(close(fd_work), 0);
+
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir",  NULL, fd_upper), 0);
+       ASSERT_EQ(close(fd_upper), 0);
+
+       for (int i = 0; i < ARRAY_SIZE(layer_fds); i++) {
+               ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[i]), 0);
+               ASSERT_EQ(close(layer_fds[i]), 0);
+       }
+
+       ASSERT_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, fd_lower), 0);
+       ASSERT_EQ(close(fd_lower), 0);
+
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
+
+       fd_overlay = sys_fsmount(fd_context, 0, 0);
+       ASSERT_GE(fd_overlay, 0);
+       ASSERT_EQ(close(fd_context), 0);
+       ASSERT_EQ(close(fd_overlay), 0);
+}
+
 TEST_HARNESS_MAIN