Backport upstream patch to install a SIGCHLD handler to reap expired ssh

child processes, preventing lots of zombies when using ControlPersist
(closes: #594687).

1 files changed, 19 insertions, 0 deletions

diff --git a/ssh.c b/ssh.c
index ab3c33d87..22d4f53c4 100644
--- a/ssh.c
+++ b/ssh.c
@@ -50,6 +50,7 @@
 #include <sys/ioctl.h>
 #include <sys/param.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 
 #include <ctype.h>
 #include <errno.h>
@@ -210,6 +211,7 @@ usage(void)
 static int ssh_session(void);
 static int ssh_session2(void);
 static void load_public_identity_files(void);
+static void main_sigchld_handler(int);
 
 /* from muxclient.c */
 void muxclient(const char *);
@@ -849,6 +851,7 @@ main(int ac, char **av)
             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 
         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
+        signal(SIGCHLD, main_sigchld_handler);
 
         /* Log into the remote system.  Never returns if the login fails. */
         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr,
@@ -1532,3 +1535,19 @@ load_public_identity_files(void)
         bzero(pwdir, strlen(pwdir));
         xfree(pwdir);
 }
+
+static void
+main_sigchld_handler(int sig)
+{
+        int save_errno = errno;
+        pid_t pid;
+        int status;
+
+        while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
+            (pid < 0 && errno == EINTR))
+                ;
+
+        signal(sig, main_sigchld_handler);
+        errno = save_errno;
+}
+