From 727056e0c9519d8eecde801e950b35f2f69c72e2 Mon Sep 17 00:00:00 2001
From: "Todd C. Miller" <Todd.Miller@sudo.ws>
Date: Fri, 23 Apr 2021 07:41:27 -0600
Subject: [PATCH] Make sure SIGCHLD is not ignored when sudo is executed. If
 SIGCHLD is ignored there is a race condition between when the process is
 executed and when the SIGCHLD handler is installed. This fixes the bug
 described by GitHub PR #98

---
 src/signal.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/signal.c b/src/signal.c
index 7f90d707b..866b64790 100644
--- a/src/signal.c
+++ b/src/signal.c
@@ -133,6 +133,18 @@ init_signals(void)
 	    case SIGTTOU:
 		/* Don't install these until exec time. */
 		break;
+	    case SIGCHLD:
+		/* Sudo needs to be able to catch SIGCHLD. */
+		if (ss->sa.sa_handler == SIG_IGN) {
+		    sudo_debug_printf(SUDO_DEBUG_INFO,
+			"will restore signal %d on exec", SIGCHLD);
+		    ss->restore = true;
+		}
+		if (sigaction(SIGCHLD, &sa, NULL) != 0) {
+		    sudo_warn(U_("unable to set handler for signal %d"),
+			SIGCHLD);
+		}
+		break;
 	    default:
 		if (ss->sa.sa_handler != SIG_IGN) {
 		    if (sigaction(ss->signo, &sa, NULL) != 0) {