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 +353,7 @@
 		pri = LOG_ERR;
 		break;
 	}
+	
 	if (txt != NULL) {
 		snprintf(fmtbuf, sizeof(fmtbuf), "%s: %s", txt, fmt);
 		vsnprintf(msgbuf, sizeof(msgbuf), fmtbuf, args);
@@ -363,6 +366,14 @@
 		snprintf(msgbuf, sizeof msgbuf, "%s\r\n", fmtbuf);
 		write(STDERR_FILENO, msgbuf, strlen(msgbuf));
 	} else {
+		/* 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 defined(HAVE_OPENLOG_R) && defined(SYSLOG_DATA_INIT)
 		openlog_r(argv0 ? argv0 : __progname, LOG_PID, log_facility, &sdata);
 		syslog_r(pri, &sdata, "%.500s", fmtbuf);
@@ -372,5 +383,6 @@
 		syslog(pri, "%.500s", fmtbuf);
 		closelog();
 #endif
+		sigprocmask(SIG_SETMASK, &oset, NULL);
 	}
 }