Merge tag 'vfs-6.15-rc1.overlayfs' of git://git.kernel.org/pub/scm/linux/kernel/git...

Pull vfs overlayfs updates from Christian Brauner:
 "Currently overlayfs uses the mounter's credentials for its
  override_creds() calls. That provides a consistent permission model.

  This patches allows a caller to instruct overlayfs to use its
  credentials instead. The caller must be located in the same user
  namespace hierarchy as the user namespace the overlayfs instance will
  be mounted in. This provides a consistent and simple security model.

  With this it is possible to e.g., mount an overlayfs instance where
  the mounter must have CAP_SYS_ADMIN but the credentials used for
  override_creds() have dropped CAP_SYS_ADMIN. It also allows the usage
  of custom fs{g,u}id different from the callers and other tweaks"

* tag 'vfs-6.15-rc1.overlayfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  selftests/ovl: add third selftest for "override_creds"
  selftests/ovl: add second selftest for "override_creds"
  selftests/filesystems: add utils.{c,h}
  selftests/ovl: add first selftest for "override_creds"
  ovl: allow to specify override credentials

diff --cc tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
index e65d95d97846dd536d3ba8f990af5022a0bf1c1b,fd1e5d7c13a3481a08d94fb7e32c20956dd909d6..5074e64e74a8a47cbb26c5a574245badc51d359a
--- 1/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
--- 2/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
+++ b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
@@@ -19,17 -24,18 +24,22 @@@ FIXTURE(set_layers_via_fds) 
  
  FIXTURE_SETUP(set_layers_via_fds)
  {
-       ASSERT_EQ(mkdir("/set_layers_via_fds", 0755), 0);
-       ASSERT_EQ(mkdir("/set_layers_via_fds_tmpfs", 0755), 0);
+       self->pidfd = -EBADF;
+       EXPECT_EQ(mkdir("/set_layers_via_fds", 0755), 0);
++      EXPECT_EQ(mkdir("/set_layers_via_fds_tmpfs", 0755), 0);
  }
  
  FIXTURE_TEARDOWN(set_layers_via_fds)
  {
+       if (self->pidfd >= 0) {
+               EXPECT_EQ(sys_pidfd_send_signal(self->pidfd, SIGKILL, NULL, 0), 0);
+               EXPECT_EQ(close(self->pidfd), 0);
+       }
        umount2("/set_layers_via_fds", 0);
-       ASSERT_EQ(rmdir("/set_layers_via_fds"), 0);
+       EXPECT_EQ(rmdir("/set_layers_via_fds"), 0);
 +
 +      umount2("/set_layers_via_fds_tmpfs", 0);
-       ASSERT_EQ(rmdir("/set_layers_via_fds_tmpfs"), 0);
++      EXPECT_EQ(rmdir("/set_layers_via_fds_tmpfs"), 0);
  }
  
  TEST_F(set_layers_via_fds, set_layers_via_fds)
@@@ -218,195 -224,302 +228,493 @@@ TEST_F(set_layers_via_fds, set_500_laye
        ASSERT_EQ(close(fd_overlay), 0);
  }
  
+ TEST_F(set_layers_via_fds, set_override_creds)
+ {
+       int fd_context, fd_tmpfs, fd_overlay;
+       int layer_fds[] = { [0 ... 3] = -EBADF };
+       pid_t pid;
+       int pidfd;
+ 
+       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);
+ 
+       ASSERT_EQ(mkdirat(fd_tmpfs, "w", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l1", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l2", 0755), 0);
+ 
+       layer_fds[0] = openat(fd_tmpfs, "w", O_DIRECTORY);
+       ASSERT_GE(layer_fds[0], 0);
+ 
+       layer_fds[1] = openat(fd_tmpfs, "u", O_DIRECTORY);
+       ASSERT_GE(layer_fds[1], 0);
+ 
+       layer_fds[2] = openat(fd_tmpfs, "l1", O_DIRECTORY);
+       ASSERT_GE(layer_fds[2], 0);
+ 
+       layer_fds[3] = openat(fd_tmpfs, "l2", O_DIRECTORY);
+       ASSERT_GE(layer_fds[3], 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_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir", NULL, layer_fds[2]), 0);
+ 
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir",   NULL, layer_fds[0]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir",  NULL, layer_fds[1]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[2]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[3]), 0);
+ 
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_STRING, "metacopy", "on", 0), 0);
+ 
+       pid = create_child(&pidfd, 0);
+       ASSERT_GE(pid, 0);
+       if (pid == 0) {
+               if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "override_creds", NULL, 0)) {
+                       TH_LOG("sys_fsconfig should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               _exit(EXIT_SUCCESS);
+       }
+       ASSERT_GE(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+       ASSERT_GE(close(pidfd), 0);
+ 
+       pid = create_child(&pidfd, 0);
+       ASSERT_GE(pid, 0);
+       if (pid == 0) {
+               if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "nooverride_creds", NULL, 0)) {
+                       TH_LOG("sys_fsconfig should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               _exit(EXIT_SUCCESS);
+       }
+       ASSERT_GE(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+       ASSERT_GE(close(pidfd), 0);
+ 
+       pid = create_child(&pidfd, 0);
+       ASSERT_GE(pid, 0);
+       if (pid == 0) {
+               if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "override_creds", NULL, 0)) {
+                       TH_LOG("sys_fsconfig should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               _exit(EXIT_SUCCESS);
+       }
+       ASSERT_GE(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+       ASSERT_GE(close(pidfd), 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(sys_move_mount(fd_overlay, "", -EBADF, "/set_layers_via_fds", MOVE_MOUNT_F_EMPTY_PATH), 0);
+ 
+       ASSERT_EQ(close(fd_context), 0);
+       ASSERT_EQ(close(fd_overlay), 0);
+ }
+ 
+ TEST_F(set_layers_via_fds, set_override_creds_invalid)
+ {
+       int fd_context, fd_tmpfs, fd_overlay, ret;
+       int layer_fds[] = { [0 ... 3] = -EBADF };
+       pid_t pid;
+       int fd_userns1, fd_userns2;
+       int ipc_sockets[2];
+       char c;
+       const unsigned int predictable_fd_context_nr = 123;
+ 
+       fd_userns1 = get_userns_fd(0, 0, 10000);
+       ASSERT_GE(fd_userns1, 0);
+ 
+       fd_userns2 = get_userns_fd(0, 1234, 10000);
+       ASSERT_GE(fd_userns2, 0);
+ 
+       ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
+       ASSERT_GE(ret, 0);
+ 
+       pid = create_child(&self->pidfd, 0);
+       ASSERT_GE(pid, 0);
+       if (pid == 0) {
+               if (close(ipc_sockets[0])) {
+                       TH_LOG("close should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               if (!switch_userns(fd_userns2, 0, 0, false)) {
+                       TH_LOG("switch_userns should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               if (read_nointr(ipc_sockets[1], &c, 1) != 1) {
+                       TH_LOG("read_nointr should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               if (close(ipc_sockets[1])) {
+                       TH_LOG("close should have succeeded");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               if (!sys_fsconfig(predictable_fd_context_nr, FSCONFIG_SET_FLAG, "override_creds", NULL, 0)) {
+                       TH_LOG("sys_fsconfig should have failed");
+                       _exit(EXIT_FAILURE);
+               }
+ 
+               _exit(EXIT_SUCCESS);
+       }
+ 
+       ASSERT_EQ(close(ipc_sockets[1]), 0);
+       ASSERT_EQ(switch_userns(fd_userns1, 0, 0, false), true);
+       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);
+ 
+       ASSERT_EQ(mkdirat(fd_tmpfs, "w", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l1", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l2", 0755), 0);
+ 
+       layer_fds[0] = openat(fd_tmpfs, "w", O_DIRECTORY);
+       ASSERT_GE(layer_fds[0], 0);
+ 
+       layer_fds[1] = openat(fd_tmpfs, "u", O_DIRECTORY);
+       ASSERT_GE(layer_fds[1], 0);
+ 
+       layer_fds[2] = openat(fd_tmpfs, "l1", O_DIRECTORY);
+       ASSERT_GE(layer_fds[2], 0);
+ 
+       layer_fds[3] = openat(fd_tmpfs, "l2", O_DIRECTORY);
+       ASSERT_GE(layer_fds[3], 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(dup3(fd_context, predictable_fd_context_nr, 0), predictable_fd_context_nr);
+       ASSERT_EQ(close(fd_context), 0);
+       fd_context = predictable_fd_context_nr;
+       ASSERT_EQ(write_nointr(ipc_sockets[0], "1", 1), 1);
+       ASSERT_EQ(close(ipc_sockets[0]), 0);
+ 
+       ASSERT_EQ(wait_for_pid(pid), 0);
+       ASSERT_EQ(close(self->pidfd), 0);
+       self->pidfd = -EBADF;
+ 
+       ASSERT_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir", NULL, layer_fds[2]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir",   NULL, layer_fds[0]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir",  NULL, layer_fds[1]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[2]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[3]), 0);
+ 
+       for (int i = 0; i < ARRAY_SIZE(layer_fds); i++)
+               ASSERT_EQ(close(layer_fds[i]), 0);
+ 
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "userxattr", NULL, 0), 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(sys_move_mount(fd_overlay, "", -EBADF, "/set_layers_via_fds", MOVE_MOUNT_F_EMPTY_PATH), 0);
+ 
+       ASSERT_EQ(close(fd_context), 0);
+       ASSERT_EQ(close(fd_overlay), 0);
+       ASSERT_EQ(close(fd_userns1), 0);
+       ASSERT_EQ(close(fd_userns2), 0);
+ }
+ 
+ TEST_F(set_layers_via_fds, set_override_creds_nomknod)
+ {
+       int fd_context, fd_tmpfs, fd_overlay;
+       int layer_fds[] = { [0 ... 3] = -EBADF };
+       pid_t pid;
+       int pidfd;
+ 
+       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);
+ 
+       ASSERT_EQ(mkdirat(fd_tmpfs, "w", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l1", 0755), 0);
+       ASSERT_EQ(mkdirat(fd_tmpfs, "l2", 0755), 0);
+ 
+       layer_fds[0] = openat(fd_tmpfs, "w", O_DIRECTORY);
+       ASSERT_GE(layer_fds[0], 0);
+ 
+       layer_fds[1] = openat(fd_tmpfs, "u", O_DIRECTORY);
+       ASSERT_GE(layer_fds[1], 0);
+ 
+       layer_fds[2] = openat(fd_tmpfs, "l1", O_DIRECTORY);
+       ASSERT_GE(layer_fds[2], 0);
+ 
+       layer_fds[3] = openat(fd_tmpfs, "l2", O_DIRECTORY);
+       ASSERT_GE(layer_fds[3], 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_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir", NULL, layer_fds[2]), 0);
+ 
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir",   NULL, layer_fds[0]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir",  NULL, layer_fds[1]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[2]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[3]), 0);
+       ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "userxattr", NULL, 0), 0);
+ 
+       pid = create_child(&pidfd, 0);
+       ASSERT_GE(pid, 0);
+       if (pid == 0) {
+               if (!cap_down(CAP_MKNOD))
+                       _exit(EXIT_FAILURE);
+ 
+               if (!cap_down(CAP_SYS_ADMIN))
+                       _exit(EXIT_FAILURE);
+ 
+               if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "override_creds", NULL, 0))
+                       _exit(EXIT_FAILURE);
+ 
+               _exit(EXIT_SUCCESS);
+       }
+       ASSERT_EQ(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+       ASSERT_GE(close(pidfd), 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(sys_move_mount(fd_overlay, "", -EBADF, "/set_layers_via_fds", MOVE_MOUNT_F_EMPTY_PATH), 0);
+       ASSERT_EQ(mknodat(fd_overlay, "dev-zero", S_IFCHR | 0644, makedev(1, 5)), -1);
+       ASSERT_EQ(errno, EPERM);
+ 
+       ASSERT_EQ(close(fd_context), 0);
+       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_F(set_layers_via_fds, set_layers_via_detached_mount_fds)
 +{
 +      int fd_context, fd_tmpfs, fd_overlay, fd_tmp;
 +      int layer_fds[] = { [0 ... 8] = -EBADF };
 +      bool layers_found[] = { [0 ... 8] =  false };
 +      size_t len = 0;
 +      char *line = NULL;
 +      FILE *f_mountinfo;
 +
 +      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);
 +
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "u/upper", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "u/work", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "l1", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "l2", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "l3", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "l4", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "d1", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "d2", 0755), 0);
 +      ASSERT_EQ(mkdirat(fd_tmpfs, "d3", 0755), 0);
 +
 +      ASSERT_EQ(sys_move_mount(fd_tmpfs, "", -EBADF, "/set_layers_via_fds_tmpfs", MOVE_MOUNT_F_EMPTY_PATH), 0);
 +
 +      fd_tmp = open_tree(fd_tmpfs, "u", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(fd_tmp, 0);
 +
 +      layer_fds[0] = openat(fd_tmp, "upper", O_CLOEXEC | O_DIRECTORY | O_PATH);
 +      ASSERT_GE(layer_fds[0], 0);
 +
 +      layer_fds[1] = openat(fd_tmp, "work", O_CLOEXEC | O_DIRECTORY | O_PATH);
 +      ASSERT_GE(layer_fds[1], 0);
 +
 +      layer_fds[2] = open_tree(fd_tmpfs, "l1", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[2], 0);
 +
 +      layer_fds[3] = open_tree(fd_tmpfs, "l2", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[3], 0);
 +
 +      layer_fds[4] = open_tree(fd_tmpfs, "l3", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[4], 0);
 +
 +      layer_fds[5] = open_tree(fd_tmpfs, "l4", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[5], 0);
 +
 +      layer_fds[6] = open_tree(fd_tmpfs, "d1", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[6], 0);
 +
 +      layer_fds[7] = open_tree(fd_tmpfs, "d2", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[7], 0);
 +
 +      layer_fds[8] = open_tree(fd_tmpfs, "d3", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
 +      ASSERT_GE(layer_fds[8], 0);
 +
 +      ASSERT_EQ(close(fd_tmpfs), 0);
 +
 +      fd_context = sys_fsopen("overlay", 0);
 +      ASSERT_GE(fd_context, 0);
 +
 +      ASSERT_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir", NULL, layer_fds[2]), 0);
 +
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir",  NULL, layer_fds[0]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir",   NULL, layer_fds[1]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[2]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[3]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[4]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[5]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "datadir+",  NULL, layer_fds[6]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "datadir+",  NULL, layer_fds[7]), 0);
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "datadir+",  NULL, layer_fds[8]), 0);
 +
 +      ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_STRING, "metacopy", "on", 0), 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(sys_move_mount(fd_overlay, "", -EBADF, "/set_layers_via_fds", MOVE_MOUNT_F_EMPTY_PATH), 0);
 +
 +      f_mountinfo = fopen("/proc/self/mountinfo", "r");
 +      ASSERT_NE(f_mountinfo, NULL);
 +
 +      while (getline(&line, &len, f_mountinfo) != -1) {
 +              char *haystack = line;
 +
 +              if (strstr(haystack, "workdir=/tmp/w"))
 +                      layers_found[0] = true;
 +              if (strstr(haystack, "upperdir=/tmp/u"))
 +                      layers_found[1] = true;
 +              if (strstr(haystack, "lowerdir+=/tmp/l1"))
 +                      layers_found[2] = true;
 +              if (strstr(haystack, "lowerdir+=/tmp/l2"))
 +                      layers_found[3] = true;
 +              if (strstr(haystack, "lowerdir+=/tmp/l3"))
 +                      layers_found[4] = true;
 +              if (strstr(haystack, "lowerdir+=/tmp/l4"))
 +                      layers_found[5] = true;
 +              if (strstr(haystack, "datadir+=/tmp/d1"))
 +                      layers_found[6] = true;
 +              if (strstr(haystack, "datadir+=/tmp/d2"))
 +                      layers_found[7] = true;
 +              if (strstr(haystack, "datadir+=/tmp/d3"))
 +                      layers_found[8] = true;
 +      }
 +      free(line);
 +
 +      for (int i = 0; i < ARRAY_SIZE(layer_fds); i++) {
 +              ASSERT_EQ(layers_found[i], true);
 +              ASSERT_EQ(close(layer_fds[i]), 0);
 +      }
 +
 +      ASSERT_EQ(close(fd_context), 0);
 +      ASSERT_EQ(close(fd_overlay), 0);
 +      ASSERT_EQ(fclose(f_mountinfo), 0);
 +}
 +
  TEST_HARNESS_MAIN