core bugfix: segfault if disk-queue file cannot be created

When using Disk Queue and a queue.filename that can not be created
by rsyslog, the service does not switch to another queue type as
supposed to and crashes at a later step.

closes: https://github.com/rsyslog/rsyslog/issues/4282

runtime/stream.c

@@ -2079,6 +2079,7 @@ static rsRetVal strmWriteChar(strm_t *__restrict__ const pThis, const uchar c)
 	if(pThis->iBufPtr == pThis->sIOBufSize) {
 		CHKiRet(strmFlushInternal(pThis, 0));
 	}
+
 	/* we now always have space for one character, so we simply copy it */
 	*(pThis->pIOBuf + pThis->iBufPtr) = c;
 	pThis->iBufPtr++;

tests/Makefile.am

@@ -289,6 +289,7 @@ TESTS +=  \
 	diskqueue.sh \
 	diskqueue-fsync.sh \
 	diskqueue-full.sh \
+	diskqueue-fail.sh \
 	diskqueue-non-unique-prefix.sh \
 	rulesetmultiqueue.sh \
 	rulesetmultiqueue-v6.sh \
@@ -1644,6 +1645,7 @@ EXTRA_DIST= \
 	diskq-rfc5424.sh \
 	rfc5424parser-sp_at_msg_start.sh \
 	diskqueue-full.sh \
+	diskqueue-fail.sh \
 	diskqueue.sh \
 	diskqueue-non-unique-prefix.sh \
 	arrayqueue.sh \

tests/diag.sh

@@ -710,7 +710,7 @@ content_count_check() {
 		grep_opt=-F
 	fi
 	file=${3:-$RSYSLOG_OUT_LOG}
-	count=$(grep -c -F -- "$1" <${RSYSLOG_OUT_LOG})
+	count=$(grep -c $grep_opt -- "$1" <${RSYSLOG_OUT_LOG})
 	if [ ${count:=0} -ne "$2" ]; then
 	    grep -c -F -- "$1" <${RSYSLOG_OUT_LOG}
 	    printf '\n============================================================\n'

tests/diskqueue-fail.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+# checks that nothing bad happens if a DA (disk) queue runs out
+# of configured disk space
+# addd 2017-02-07 by RGerhards, released under ASL 2.0
+. ${srcdir:=.}/diag.sh init
+export NUMMESSAGES=100
+generate_conf
+add_conf '
+module(	load="../plugins/imtcp/.libs/imtcp")
+input(type="imtcp" port="0" listenPortFileName="'$RSYSLOG_DYNNAME'.tcpflood_port" ruleset="queuefail")
+
+template(name="outfmt" type="string"
+	 string="%msg:F,58:2%,%msg:F,58:3%,%msg:F,58:4%\n")
+
+ruleset(
+	name="queuefail"
+	queue.type="Disk"
+	queue.filename="fssailstocreate"
+	queue.maxDiskSpace="4m"
+	queue.maxfilesize="1m"
+	queue.timeoutenqueue="300000"
+	queue.lowwatermark="5000"
+) {
+	action(type="omfile" template="outfmt" file="'$RSYSLOG_OUT_LOG'")
+}
+'
+startup
+
+tcpflood -p$TCPFLOOD_PORT -m$NUMMESSAGES
+
+shutdown_when_empty
+wait_shutdown
+seq_check
+
+exit_test

tools/rsyslogd.c

@@ -808,12 +808,17 @@ rsRetVal createMainQueue(qqueue_t **ppQueue, uchar *pszQueueName, struct nvlst *
 }
 
 rsRetVal
-startMainQueue(qqueue_t *pQueue)
+startMainQueue(qqueue_t *const pQueue)
 {
 	DEFiRet;
 	CHKiRet_Hdlr(qqueueStart(pQueue)) {
 		/* no queue is fatal, we need to give up in that case... */
-		LogError(0, iRet, "could not start (ruleset) main message queue"); \
+		LogError(0, iRet, "could not start (ruleset) main message queue");
+		pQueue->qType = QUEUETYPE_DIRECT;
+		CHKiRet_Hdlr(qqueueStart(pQueue)) {
+			/* no queue is fatal, we need to give up in that case... */
+			LogError(0, iRet, "fatal error: could not even start queue in direct mode");
+		}
 	}
 	RETiRet;
 }