log: fix infinite loop with multiple lxc.log.syslog keys

This caused the linked list of appenders to loop on itself, creating
an infinite logging loop in `__lxc_log_append`.

Signed-off-by: Felix Abecassis <fabecassis@nvidia.com>

diff --git a/src/lxc/log.c b/src/lxc/log.c
index 351b191fb93d938d92e712db9a75d8b474009ef5..b62aeb8d222615ab55739229c1cd2781130e32c1 100644 (file)
--- a/src/lxc/log.c
+++ b/src/lxc/log.c
@@ -533,6 +533,17 @@ extern int lxc_log_syslog(int facility)
                lxc_log_category_lxc.appender = &log_appender_syslog;
                return 0;
        }
+
+       appender = lxc_log_category_lxc.appender;
+       /* Check if syslog was already added, to avoid creating a loop */
+       while (appender) {
+               if (appender == &log_appender_syslog) {
+                       /* not an error: openlog re-opened the connection */
+                       return 0;
+               }
+               appender = appender->next;
+       }
+
        appender = lxc_log_category_lxc.appender;
        while (appender->next != NULL)
                appender = appender->next;