rwsig/update_fw: Prevent race in rollback protection
There is a window where the rollback information in RW could
potentially be updated during RW signature verification. We make
sure this cannot happen by:
- Preventing update over USB while RWSIG is running
- When system is locked, only update rollback information if
RW region is locked: this guarantees that RW cannot be modified
from boot until RW is validated, and then until rollback
information is updated.
Also, remove rollback_lock() in rwsig_check_signature:
rwsig_jump_now() protects all flash, which also protects rollback.
This reduces the number of required reboots on rollback update.
BRANCH=none
BUG=b:35586219
BUG=b:35587171
TEST=Add long delay in rwsig_check_signature, make sure EC cannot
be updated while verification is in progress.
Change-Id: I7a51fad8a64b7e258b3a7e15d75b3dab64ce1c94
Reviewed-on: https://chromium-review.googlesource.com/479176
Commit-Ready: Nicolas Boichat <drinkcat@chromium.org>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
3 files changed
