tree ee2709f66298be280e0a51c524e2f2777e7dbbbe
parent a9b5d8c8eec4534c3433466fc6766ede675d16ce
author Kelvin Zhang <zhangkelvin@google.com> 1619459089 -0400
committer Kelvin Zhang <zhangkelvin@google.com> 1620309491 -0400

Fix verity discarded bug

If update_engine opens CowWriterFileDescriptor w/o writing anything,
data past the resume label is readable while fd is open, but will
be discarded once the fd is closed. Such "phantom read" causes
inconsistency. This CL contains two changes to address the above bug:

1. When device reboots after update, all I/O are served by snapuserd.
update_engine should use snapuserd for verification to emulate bahvior
of device after reboot.

2. When a CowWriterFd is opened, don't call Finalize() if no verity is
written. Since past-the-end data is discarded when we call Finalize()

Test: th

Bug: 186196758

Change-Id: Ia1d31b671c16fded7319677fe0397f1288457201