From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Tue, 20 Jun 2023 22:20:30 +0000 (+0300)
Subject: lib: Fix potential log corruption with event_set_log_message_callback()
X-Git-Tag: 2.4.0~2671
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4e054549b0b0d51f27655efa79c3a1e0647b9a43;p=thirdparty%2Fdovecot%2Fcore.git

lib: Fix potential log corruption with event_set_log_message_callback()

If the callback returned the same input log_prefix pointer back, the message
became corrupted because the log_prefix was soon changed.
---

diff --git a/src/lib/event-log.c b/src/lib/event-log.c
index c738ea2b3b..af0b0576a5 100644
--- a/src/lib/event-log.c
+++ b/src/lib/event-log.c
@@ -192,20 +192,27 @@ event_get_log_message(struct event *event,
 
 		/* construct the log message composed by children and arguments
 		 */
+		const char *log_prefix = str_c(glmctx->log_prefix);
 		if (glmctx->message == NULL) {
 			str_vprintfa(glmctx->log_prefix, fmt, args);
-			in_message = str_c(glmctx->log_prefix);
+			in_message = log_prefix;
 		} else if (str_len(glmctx->log_prefix) == 0) {
 			in_message = glmctx->message;
 		} else {
 			str_append(glmctx->log_prefix, glmctx->message);
-			in_message = str_c(glmctx->log_prefix);
+			in_message = log_prefix;
 		}
 
 		/* reformat the log message */
 		glmctx->message = event->log_message_callback(
 			event->log_message_callback_context,
 			glmctx->params->log_type, in_message);
+		if (glmctx->message == log_prefix) {
+			/* The log message returned the input log_prefix
+			   pointer. However, it's going to become modified, so
+			   it needs to be duplicated. */
+			glmctx->message = t_strdup(log_prefix);
+		}
 
 		/* continue with a cleared prefix buffer (as prefix is now part
 		   of *message_r). */