tree b9d70ffd007e07b3a52c3703b5549a68ccc4eba3
parent 9a3fbe116209a6d44a5f9672a3a249cb8932e3d2
author Hugo Benichi <hugobenichi@google.com> 1466470087 +0900
committer Lorenzo Colitti <lorenzo@google.com> 1468328200 +0900

Fix unsafe concurrent access in LegacyTypeTracker

This patch adds synchronization inside LegacyTypeTracker so that
getNetworkForType() can safely run concurrently with remove().

Without synchronization if remove() removes the last network for a
given type while getNetworkForType() runs for the same type, it is
possible that getNetworkForType tries to access the head of an empty
list, resulting in a runtime exception.

This issue was found by zoran.jovanovic@sonymobile.com who proposed a
fix in AOSP (Change-Id: Ia963662edb9d643790e8d9439e4dbdcac4c2187b).

This patch differs from the fix proposed by the bug reporter and tries
instead to do the minimum amount of locking to make getNetworkForType
safe.

Bug: 29030387

(cherry picked from commit 78caa25870391f676e1edbd448b5ff3e12a99a1e)

Change-Id: I915aac527fc8828b32bf35fee870add2dfb11d8d