init: set the sys.use_memfd property to false

The sys.use_memfd property is set by default to false in Android
to temporarily disable memfd, till vendor and apps are ready for it.
The main issue: either apps or vendor processes can directly make ashmem
IOCTLs on FDs they receive by assuming they are ashmem, without going
through libcutils. Such fds could have very well be originally created with
libcutils hence they could be memfd. Thus the IOCTLs will break.

Set default value of sys.use_memfd property to true once the issue is
resolved, so that the code can then self-detect if kernel support is present
on the device. The property can also set to true from adb shell, for
debugging.

Bug: 113362644

Change-Id: I0f572ef36cac2a58fe308ddb90bbeffbecdaed3b
Signed-off-by: Joel Fernandes <joelaf@google.com>

rootdir/init.rc

@@ -593,6 +593,11 @@ on post-fs-data
     # Set indication (checked by vold) that we have finished this action
     #setprop vold.post_fs_data_done 1
 
+    # sys.memfd_use set to false by default, which keeps it disabled
+    # until it is confirmed that apps and vendor processes don't make
+    # IOCTLs on ashmem fds any more.
+    setprop sys.use_memfd false
+
 # It is recommended to put unnecessary data/ initialization from post-fs-data
 # to start-zygote in device's init.rc to unblock zygote start.
 on zygote-start && property:ro.crypto.state=unencrypted