From: Jiri Vymazal <jvymazal@redhat.com>
Date: Wed, 18 Dec 2019 09:48:15 +0100
Subject: [PATCH] Fix race condition related to libfastjson when using DA queue

Rsyslogd aborts when writing to disk queue from multiple workers simultaneously.
It is assumed that libfastjson is not thread-safe.
Resolve libfastjson race condition when writing to disk queue.

see also https://github.com/rsyslog/rsyslog/issues/4099
---
 runtime/msg.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/runtime/msg.c b/runtime/msg.c
index b5c17cfdd4..f9da40005f 100644
--- a/runtime/msg.c
+++ b/runtime/msg.c
@@ -1211,11 +1211,15 @@ static rsRetVal MsgSerialize(smsg_t *pThis, strm_t *pStrm)
 	psz = pThis->pszStrucData; 
 	CHKiRet(obj.SerializeProp(pStrm, UCHAR_CONSTANT("pszStrucData"), PROPTYPE_PSZ, (void*) psz));
 	if(pThis->json != NULL) {
+		MsgLock(pThis);
 		psz = (uchar*) json_object_get_string(pThis->json);
+		MsgUnlock(pThis);
 		CHKiRet(obj.SerializeProp(pStrm, UCHAR_CONSTANT("json"), PROPTYPE_PSZ, (void*) psz));
 	}
 	if(pThis->localvars != NULL) {
+		MsgLock(pThis);
 		psz = (uchar*) json_object_get_string(pThis->localvars);
+		MsgUnlock(pThis);
 		CHKiRet(obj.SerializeProp(pStrm, UCHAR_CONSTANT("localvars"), PROPTYPE_PSZ, (void*) psz));
 	}