From a1c9327e0be389ee0ed9e4171767f00e98139969 Mon Sep 17 00:00:00 2001
From: "Wladimir J. van der Laan" <laanwj@gmail.com>
Date: Mon, 28 May 2018 16:06:53 +0200
Subject: [PATCH] Merge #13300: qa: Initialize lockstack to prevent null
 pointer deref

fa9da85b7cc759d06bc24854be2bad0ea87b6006 qa: Initialize lockstack to prevent null pointer deref (MarcoFalke)

Pull request description:

  It is currently impossible to call debug methods such as `AssertLock(Not)Held` on a thread without running into undefined behavior, unless a lock was pushed on the stack in this thread.

  Initializing the global `lockstack` seems to fix both issues.

Tree-SHA512: 8cb76b22cb31887ddf15742fdc790f01e8f04ed837367d0fd4996535748d124342e8bfde68952b903847b96ad33406c64907a53ebab9646f78d97fa4365c3061
---
 src/sync.cpp | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/sync.cpp b/src/sync.cpp
index 96df74a778..0409ed2911 100644
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -72,7 +72,7 @@ struct LockData {
     std::mutex dd_mutex;
 } static lockdata;
 
-static thread_local std::unique_ptr<LockStack> lockstack;
+static thread_local LockStack g_lockstack;
 
 static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch, const LockStack& s1, const LockStack& s2)
 {
@@ -107,21 +107,18 @@ static void potential_deadlock_detected(const std::pair<void*, void*>& mismatch,
 
 static void push_lock(void* c, const CLockLocation& locklocation)
 {
-    if (!lockstack)
-        lockstack.reset(new LockStack);
-
     std::lock_guard<std::mutex> lock(lockdata.dd_mutex);
 
-    lockstack->push_back(std::make_pair(c, locklocation));
+    g_lockstack.push_back(std::make_pair(c, locklocation));
 
-    for (const std::pair<void*, CLockLocation> & i : (*lockstack)) {
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack) {
         if (i.first == c)
             break;
 
         std::pair<void*, void*> p1 = std::make_pair(i.first, c);
         if (lockdata.lockorders.count(p1))
             continue;
-        lockdata.lockorders[p1] = (*lockstack);
+        lockdata.lockorders[p1] = g_lockstack;
 
         std::pair<void*, void*> p2 = std::make_pair(c, i.first);
         lockdata.invlockorders.insert(p2);
@@ -132,7 +129,7 @@ static void push_lock(void* c, const CLockLocation& locklocation)
 
 static void pop_lock()
 {
-    (*lockstack).pop_back();
+    g_lockstack.pop_back();
 }
 
 void EnterCritical(const char* pszName, const char* pszFile, int nLine, void* cs, bool fTry)
@@ -148,14 +145,14 @@ void LeaveCritical()
 std::string LocksHeld()
 {
     std::string result;
-    for (const std::pair<void*, CLockLocation> & i : *lockstack)
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack)
         result += i.second.ToString() + std::string("\n");
     return result;
 }
 
 void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 {
-    for (const std::pair<void*, CLockLocation> & i : *lockstack)
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack)
         if (i.first == cs)
             return;
     fprintf(stderr, "Assertion failed: lock %s not held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
@@ -164,7 +161,7 @@ void AssertLockHeldInternal(const char* pszName, const char* pszFile, int nLine,
 
 void AssertLockNotHeldInternal(const char* pszName, const char* pszFile, int nLine, void* cs)
 {
-    for (const std::pair<void*, CLockLocation>& i : *lockstack) {
+    for (const std::pair<void*, CLockLocation>& i : g_lockstack) {
         if (i.first == cs) {
             fprintf(stderr, "Assertion failed: lock %s held in %s:%i; locks held:\n%s", pszName, pszFile, nLine, LocksHeld().c_str());
             abort();