bugfix: invalid buffer write in (file) stream class

currently being accessed buffer could be overwritten with new data.
While this probably did not cause access violations, it could case loss
and/or duplication of some data (definitely a race with no deterministic
outcome)

2 files changed, 7 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 672c69ae..85a9ecb6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,11 @@ Version 4.6.2  [v4-stable] (rgerhards), 2010-03-??
   to ease migration from syslog-ng. See property replacer doc for
   details. [backport from 5.5.3 because urgently needed by some]
 - improved testbench
+- bugfix: invalid buffer write in (file) stream class
+  currently being accessed buffer could be overwritten with new data.
+  While this probably did not cause access violations, it could case loss
+  and/or duplication of some data (definitely a race with no deterministic
+  outcome)
 - bugfix: potential hang condition during filestream close
   predicate was not properly checked when waiting for the background file
   writer
diff --git a/runtime/stream.c b/runtime/stream.c
index 88606db7..e2f6623e 100644
--- a/runtime/stream.c
+++ b/runtime/stream.c
@@ -863,7 +863,8 @@ doAsyncWriteInternal(strm_t *pThis, size_t lenBuf)
 	DEFiRet;
 	ISOBJ_TYPE_assert(pThis, strm);
 
-	while(pThis->iCnt >= STREAM_ASYNC_NUMBUFS)
+	/* the -1 below is important, because we need one buffer for the main thread! */
+	while(pThis->iCnt >= STREAM_ASYNC_NUMBUFS - 1)
 		d_pthread_cond_wait(&pThis->notFull, &pThis->mut);
 
 	pThis->asyncBuf[pThis->iEnq % STREAM_ASYNC_NUMBUFS].lenBuf = lenBuf;