From 9551cd05357925e8bec8e0030d5f98fd07f17839 Mon Sep 17 00:00:00 2001
From: Victor Julien <victor@inliniac.net>
Date: Wed, 18 Aug 2021 20:14:48 +0200
Subject: [PATCH] threading: don't pass locked flow between threads

Previously the flow manager would share evicted flows with the workers
while keeping the flows mutex locked. This reduced the number of unlock/
lock cycles while there was guaranteed to be no contention.

This turns out to be undefined behavior. A lock is supposed to be locked
and unlocked from the same thread. It appears that FreeBSD is stricter on
this than Linux.

This patch addresses the issue by unlocking before handing a flow off
to another thread, and locking again from the new thread.

Issue was reported and largely analyzed by Bill Meeks.

Bug: #4478
---
 src/flow-hash.c    | 1 +
 src/flow-manager.c | 2 +-
 src/flow-timeout.c | 1 +
 src/flow-worker.c  | 1 +
 4 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/flow-hash.c b/src/flow-hash.c
index 10b59ae2d4..70416aa538 100644
--- a/src/flow-hash.c
+++ b/src/flow-hash.c
@@ -692,6 +692,7 @@ static inline void MoveToWorkQueue(ThreadVars *tv, FlowLookupStruct *fls,
         f->fb = NULL;
         f->next = NULL;
         FlowQueuePrivateAppendFlow(&fls->work_queue, f);
+        FLOWLOCK_UNLOCK(f);
     } else {
         /* implied: TCP but our thread does not own it. So set it
          * aside for the Flow Manager to pick it up. */
diff --git a/src/flow-manager.c b/src/flow-manager.c
index b2a869ccd5..1d4306a90e 100644
--- a/src/flow-manager.c
+++ b/src/flow-manager.c
@@ -333,9 +333,9 @@ static uint32_t ProcessAsideQueue(FlowManagerTimeoutThread *td, FlowTimeoutCount
                 FlowForceReassemblyNeedReassembly(f) == 1)
         {
             FlowForceReassemblyForFlow(f);
+            FLOWLOCK_UNLOCK(f);
             /* flow ownership is passed to the worker thread */
 
-            /* flow remains locked */
             counters->flows_aside_needs_work++;
             continue;
         }
diff --git a/src/flow-timeout.c b/src/flow-timeout.c
index 972b35076b..d6cca49008 100644
--- a/src/flow-timeout.c
+++ b/src/flow-timeout.c
@@ -401,6 +401,7 @@ static inline void FlowForceReassemblyForHash(void)
                 RemoveFromHash(f, prev_f);
                 f->flow_end_flags |= FLOW_END_FLAG_SHUTDOWN;
                 FlowForceReassemblyForFlow(f);
+                FLOWLOCK_UNLOCK(f);
                 f = next_f;
                 continue;
             }
diff --git a/src/flow-worker.c b/src/flow-worker.c
index 69dbb6ac57..dccf3581dd 100644
--- a/src/flow-worker.c
+++ b/src/flow-worker.c
@@ -168,6 +168,7 @@ static void CheckWorkQueue(ThreadVars *tv, FlowWorkerThreadData *fw,
 {
     Flow *f;
     while ((f = FlowQueuePrivateGetFromTop(fq)) != NULL) {
+        FLOWLOCK_WRLOCK(f);
         f->flow_end_flags |= FLOW_END_FLAG_TIMEOUT; //TODO emerg
 
         const FlowStateType state = f->flow_state;
-- 
2.47.2