oeqa/selftest: Add lower layer test for overlayfs-etc

Place a test file on the /etc by means of overlayfs-user recipe.
Perform QA checks to make sure that:
- When lower layer is exposed, that it's read-only to avoid undefined behavior
- By default lower layer is not exposed

(From OE-Core rev: 2fc742178675598208b400d9889a1681249d7eea)

Signed-off-by: Vyacheslav Yurkov <v.yurkov@precitec.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 74 insertions, 23 deletions

diff --git a/meta-selftest/recipes-test/overlayfs-user/overlayfs-user.bb b/meta-selftest/recipes-test/overlayfs-user/overlayfs-user.bb
index 913a4d1fdb..50cba9514b 100644
--- a/meta-selftest/recipes-test/overlayfs-user/overlayfs-user.bb
+++ b/meta-selftest/recipes-test/overlayfs-user/overlayfs-user.bb
@@ -12,6 +12,11 @@ OVERLAYFS_WRITABLE_PATHS[mnt-overlay] += "/usr/share/my-application"
 
 do_install() {
     install -d ${D}/usr/share/my-application
+    install -d ${D}${sysconfdir}
+    echo "Original file in /etc" >> ${D}${sysconfdir}/lower-layer-test.txt
 }
 
-FILES:${PN} += "/usr"
+FILES:${PN} += "\
+    ${exec_prefix} \
+    ${sysconfdir \
+"
diff --git a/meta/lib/oeqa/selftest/cases/overlayfs.py b/meta/lib/oeqa/selftest/cases/overlayfs.py
index f550015b4b..57a8c8bdb6 100644
--- a/meta/lib/oeqa/selftest/cases/overlayfs.py
+++ b/meta/lib/oeqa/selftest/cases/overlayfs.py
@@ -381,28 +381,7 @@ OVERLAYFS_ETC_DEVICE = "/dev/sda3"
         Author:    Vyacheslav Yurkov <uvv.mail@gmail.com>
         """
 
-        config = """
-DISTRO_FEATURES:append = " systemd"
-
-# Use systemd as init manager
-VIRTUAL-RUNTIME_init_manager = "systemd"
-
-# enable overlayfs in the kernel
-KERNEL_EXTRA_FEATURES:append = " features/overlayfs/overlayfs.scc"
-
-IMAGE_FSTYPES += "wic"
-OVERLAYFS_INIT_OPTION = "{OVERLAYFS_INIT_OPTION}"
-WKS_FILE = "overlayfs_etc.wks.in"
-
-EXTRA_IMAGE_FEATURES += "read-only-rootfs"
-# Image configuration for overlayfs-etc
-EXTRA_IMAGE_FEATURES += "overlayfs-etc"
-IMAGE_FEATURES:remove = "package-management"
-OVERLAYFS_ETC_MOUNT_POINT = "/data"
-OVERLAYFS_ETC_FSTYPE = "ext4"
-OVERLAYFS_ETC_DEVICE = "/dev/sda3"
-OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "{OVERLAYFS_ETC_USE_ORIG_INIT_NAME}"
-"""
+        config = self.get_working_config()
 
         args = {
             'OVERLAYFS_INIT_OPTION': "" if origInit else "init=/sbin/preinit",
@@ -423,6 +402,11 @@ OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "{OVERLAYFS_ETC_USE_ORIG_INIT_NAME}"
             line = getline_qemu(output, "upperdir=/data/overlay-etc/upper")
             self.assertTrue(line and line.startswith("/data/overlay-etc/upper on /etc type overlay"), msg=output)
 
+            # check that lower layer is not available
+            status, output = qemu.run_serial("ls -1 /data/overlay-etc/lower")
+            line = getline_qemu(output, "No such file or directory")
+            self.assertTrue(line, msg=output)
+
             status, output = qemu.run_serial("touch " + testFile)
             status, output = qemu.run_serial("sync")
             status, output = qemu.run_serial("ls -1 " + testFile)
@@ -434,3 +418,65 @@ OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "{OVERLAYFS_ETC_USE_ORIG_INIT_NAME}"
             status, output = qemu.run_serial("ls -1 " + testFile)
             line = getline_qemu(output, testFile)
             self.assertTrue(line and line.startswith(testFile), msg=output)
+
+    def test_lower_layer_access(self):
+        """
+        Summary:   Test that lower layer of /etc is available read-only when configured
+        Expected:  Can't write to lower layer. The files on lower and upper different after
+                   modification
+        Author:    Vyacheslav Yurkov <uvv.mail@gmail.com>
+        """
+
+        config = self.get_working_config()
+
+        configLower = """
+OVERLAYFS_ETC_EXPOSE_LOWER = "1"
+IMAGE_INSTALL:append = " overlayfs-user"
+"""
+        testFile = "lower-layer-test.txt"
+
+        args = {
+            'OVERLAYFS_INIT_OPTION': "",
+            'OVERLAYFS_ETC_USE_ORIG_INIT_NAME': 1
+        }
+
+        self.write_config(config.format(**args))
+
+        self.append_config(configLower)
+        bitbake('core-image-minimal')
+
+        with runqemu('core-image-minimal', image_fstype='wic') as qemu:
+            status, output = qemu.run_serial("echo \"Modified in upper\" > /etc/" + testFile)
+            status, output = qemu.run_serial("diff /etc/" + testFile + " /data/overlay-etc/lower/" + testFile)
+            line = getline_qemu(output, "Modified in upper")
+            self.assertTrue(line, msg=output)
+            line = getline_qemu(output, "Original file")
+            self.assertTrue(line, msg=output)
+
+            status, output = qemu.run_serial("touch /data/overlay-etc/lower/ro-test.txt")
+            line = getline_qemu(output, "Read-only file system")
+            self.assertTrue(line, msg=output)
+
+    def get_working_config(self):
+        return """
+DISTRO_FEATURES:append = " systemd"
+
+# Use systemd as init manager
+VIRTUAL-RUNTIME_init_manager = "systemd"
+
+# enable overlayfs in the kernel
+KERNEL_EXTRA_FEATURES:append = " features/overlayfs/overlayfs.scc"
+
+IMAGE_FSTYPES += "wic"
+OVERLAYFS_INIT_OPTION = "{OVERLAYFS_INIT_OPTION}"
+WKS_FILE = "overlayfs_etc.wks.in"
+
+EXTRA_IMAGE_FEATURES += "read-only-rootfs"
+# Image configuration for overlayfs-etc
+EXTRA_IMAGE_FEATURES += "overlayfs-etc"
+IMAGE_FEATURES:remove = "package-management"
+OVERLAYFS_ETC_MOUNT_POINT = "/data"
+OVERLAYFS_ETC_FSTYPE = "ext4"
+OVERLAYFS_ETC_DEVICE = "/dev/sda3"
+OVERLAYFS_ETC_USE_ORIG_INIT_NAME = "{OVERLAYFS_ETC_USE_ORIG_INIT_NAME}"
+"""