init: Add an selinux transition for snapuserd.
With compressed VAB updates, it is not possible to mount /system without
first running snapuserd, which is the userspace component to the dm-user
kernel module. This poses a problem because as soon as selinux
enforcement is enabled, snapuserd (running in a kernel context) does not
have access to read and decompress the underlying system partition.
To account for this, we split SelinuxInitialize into multiple steps:
First, sepolicy is read into an in-memory string.
Second, the device-mapper tables for all snapshots are rebuilt. This
flushes any pending reads and creates new dm-user devices. The original
kernel-privileged snapuserd is then killed.
Third, sepolicy is loaded from the in-memory string.
Fourth, we re-launch snapuserd and connect it to the newly created
dm-user devices. As part of this step we restorecon device-mapper
devices and /dev/block/by-name/super, since the new snapuserd is in a
limited context.
Finally, we set enforcing mode.
This sequence ensures that snapuserd has appropriate privileges with a
minimal number of permissive audits.
Bug: 173476209
Test: full OTA with VABC applies and boots
Change-Id: Ie4e0f5166b01c31a6f337afc26fc58b96217604e
diff --git a/init/Android.bp b/init/Android.bp
index 19ba21b..cd295cf 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -60,6 +60,7 @@
"selabel.cpp",
"selinux.cpp",
"sigchld_handler.cpp",
+ "snapuserd_transition.cpp",
"switch_root.cpp",
"uevent_listener.cpp",
"ueventd.cpp",