From 84abb87fd83ad7a162ea143fdad87392a65b57d2 Mon Sep 17 00:00:00 2001
From: Rahul Frias <rfrias@google.com>
Date: Fri, 19 Nov 2021 13:00:11 -0800
Subject: [PATCH] Protect against race conditions when adding a license

[ Merge of http://go/wvgerrit/142249 and http://go/ag/16307264 ]

This adds concurrency protection to a session when policy
timers are reset to from v15 to v16. The v15 policy timer may still be
in use by the decryption thread.

Bug: 204282907
Bug: 207304220
Test: Unit/Integration tests, GtsMediaTestCases
Change-Id: I4967b3927e47733fb23a1a12b6094d1cd2072918
---
 libwvdrmengine/cdm/core/src/cdm_engine.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libwvdrmengine/cdm/core/src/cdm_engine.cpp b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
index 132d2e4c..014ac290 100644
--- a/libwvdrmengine/cdm/core/src/cdm_engine.cpp
+++ b/libwvdrmengine/cdm/core/src/cdm_engine.cpp
@@ -387,7 +387,16 @@ CdmResponseType CdmEngine::AddKey(const CdmSessionId& session_id,
     return EMPTY_KEY_DATA_1;
   }
 
-  const CdmResponseType sts = session->AddKey(key_data);
+  CdmResponseType sts = KEY_ADDED;
+  {
+    // TODO(rfrias): Refactor. For now lock while adding keys to prevent
+    // a race condition between this and the decryption thread. This may
+    // occur if |policy_timers_| is reset when PolicyEngine::SetLicense
+    // is called.
+    std::unique_lock<std::recursive_mutex> lock(session_map_lock_);
+    sts = session->AddKey(key_data);
+  }
+
   if (sts == KEY_ADDED) {
     if (session->is_release()) {
       *license_type = kLicenseTypeRelease;