Test that detached mount trees receive propagation events.
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
.../selftests/mount_setattr/mount_setattr_test.c | 70 ++++++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/tools/testing/selftests/mount_setattr/mount_setattr_test.c b/tools/testing/selftests/mount_setattr/mount_setattr_test.c
index 1e0508cb5c2d..33fa1f53fdf5 100644
--- a/tools/testing/selftests/mount_setattr/mount_setattr_test.c
+++ b/tools/testing/selftests/mount_setattr/mount_setattr_test.c
@@ -2097,4 +2097,74 @@ TEST_F(mount_setattr, two_detached_subtrees_of_same_anonymous_mount_namespace)
ASSERT_EQ(move_mount(fd_tree1, "", -EBADF, "/tmp/target1", MOVE_MOUNT_F_EMPTY_PATH), 0);
}
+TEST_F(mount_setattr, detached_tree_propagation)
+{
+ int fd_tree = -EBADF;
+ struct statx stx1, stx2, stx3, stx4;
+
+ ASSERT_EQ(unshare(CLONE_NEWNS), 0);
+ ASSERT_EQ(mount(NULL, "/mnt", NULL, MS_REC | MS_SHARED, NULL), 0);
+
+ /*
+ * Copy the following mount tree:
+ *
+ * /mnt testing tmpfs
+ * |-/mnt/A testing tmpfs
+ * | `-/mnt/A/AA testing tmpfs
+ * | `-/mnt/A/AA/B testing tmpfs
+ * | `-/mnt/A/AA/B/BB testing tmpfs
+ * `-/mnt/B testing ramfs
+ */
+ fd_tree = sys_open_tree(-EBADF, "/mnt",
+ AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |
+ AT_RECURSIVE | OPEN_TREE_CLOEXEC |
+ OPEN_TREE_CLONE);
+ ASSERT_GE(fd_tree, 0);
+
+ ASSERT_EQ(statx(-EBADF, "/mnt/A", 0, 0, &stx1), 0);
+ ASSERT_EQ(statx(fd_tree, "A", 0, 0, &stx2), 0);
+
+ /*
+ * Copying the mount namespace like done above doesn't alter the
+ * mounts in any way so the filesystem mounted on /mnt must be
+ * identical even though the mounts will differ. Use the device
+ * information to verify that. Note that tmpfs will have a 0
+ * major number so comparing the major number is misleading.
+ */
+ ASSERT_EQ(stx1.stx_dev_minor, stx2.stx_dev_minor);
+
+ /* Mount a tmpfs filesystem over /mnt/A. */
+ ASSERT_EQ(mount(NULL, "/mnt/A", "tmpfs", 0, NULL), 0);
+
+
+ ASSERT_EQ(statx(-EBADF, "/mnt/A", 0, 0, &stx3), 0);
+ ASSERT_EQ(statx(fd_tree, "A", 0, 0, &stx4), 0);
+
+ /*
+ * A new filesystem has been mounted on top of /mnt/A which
+ * means that the device information will be different for any
+ * statx() that was taken from /mnt/A before the mount compared
+ * to one after the mount.
+ *
+ * Since we already now that the device information between the
+ * stx1 and stx2 samples are identical we also now that stx2 and
+ * stx3 device information will necessarily differ.
+ */
+ ASSERT_NE(stx1.stx_dev_minor, stx3.stx_dev_minor);
+
+ /*
+ * If mount propagation worked correctly then the tmpfs mount
+ * that was created after the mount namespace was unshared will
+ * have propagated onto /mnt/A in the detached mount tree.
+ *
+ * Verify that the device information for stx3 and stx4 are
+ * identical. It is already established that stx3 is different
+ * from both stx1 and stx2 sampled before the tmpfs mount was
+ * done so if stx3 and stx4 are identical the proof is done.
+ */
+ ASSERT_EQ(stx3.stx_dev_minor, stx4.stx_dev_minor);
+
+ EXPECT_EQ(close(fd_tree), 0);
+}
+
TEST_HARNESS_MAIN
--
2.47.2
