openssh/openssh-4.6p1-blocksigalrm.diff

--- log.c
+++ log.c
@@ -50,6 +50,7 @@
 
 #include "xmalloc.h"
 #include "log.h"
+#include <signal.h>
 
 static LogLevel log_level = SYSLOG_LEVEL_INFO;
 static int log_on_stderr = 1;
@@ -313,6 +314,7 @@
 	char fmtbuf[MSGBUFSIZ];
 	char *txt = NULL;
 	int pri = LOG_INFO;
+	sigset_t nset, oset;
 
 	if (level > log_level)
 		return;
@@ -351,6 +353,15 @@
 		pri = LOG_ERR;
 		break;
 	}
+	/* Prevent a race between the grace_alarm
+	 * which writes a log message and terminates
+	 * and main sshd code that leads to deadlock 
+	 * as syslog is not async safe.
+	 */ 
+	sigemptyset(&nset);
+	sigaddset(&nset, SIGALRM);
+	sigprocmask(SIG_BLOCK, &nset, &oset);
+
 	if (txt != NULL) {
 		snprintf(fmtbuf, sizeof(fmtbuf), "%s: %s", txt, fmt);
 		vsnprintf(msgbuf, sizeof(msgbuf), fmtbuf, args);
@@ -372,5 +383,7 @@
 		syslog(pri, "%.500s", fmtbuf);
 		closelog();
 #endif
+
 	}
+	sigprocmask(SIG_SETMASK, &oset, NULL);
 }