mRecentPositions must be protected by the master lock.

src/ripple_app/consensus/LedgerConsensus.cpp

@@ -520,7 +520,7 @@ public:
                         &getApp().getInboundLedgers(),
                         mPrevLedgerHash, 0, InboundLedger::fcCONSENSUS));
                 mHaveCorrectLCL = false;
-	    }
+            }
             return;
         }
 
@@ -851,15 +851,16 @@ private:
     */
     void accept (SHAMap::pointer set)
     {
-        if (set->getHash ().isNonZero ()) 
-        // put our set where others can get it later    
-            getApp().getOPs ().takePosition (mPreviousLedger
-                ->getLedgerSeq (), set);
 
         {
             Application::ScopedLockType lock 
                 (getApp ().getMasterLock ());
 
+            // put our set where others can get it later
+            if (set->getHash ().isNonZero ())
+               getApp().getOPs ().takePosition (
+                   mPreviousLedger->getLedgerSeq (), set);
+
             assert (set->getHash () == mOurPosition->getCurrentHash ());
             // these are now obsolete
             getApp().getOPs ().peekStoredProposals ().clear (); 

src/ripple_app/misc/NetworkOPs.cpp

@@ -1561,6 +1561,7 @@ void NetworkOPsImp::processTrustedProposal (LedgerProposal::pointer proposal,
     }
 }
 
+// Must be called while holding the master lock
 SHAMap::pointer NetworkOPsImp::getTXMap (uint256 const& hash)
 {
     std::map<uint256, std::pair<int, SHAMap::pointer> >::iterator it = mRecentPositions.find (hash);
@@ -1574,6 +1575,7 @@ SHAMap::pointer NetworkOPsImp::getTXMap (uint256 const& hash)
     return mConsensus->getTransactionTree (hash, false);
 }
 
+// Must be called while holding the master lock
 void NetworkOPsImp::takePosition (int seq, SHAMap::ref position)
 {
     mRecentPositions[position->getHash ()] = std::make_pair (seq, position);