Index: lib/libc/gen/posix_spawn.c
===================================================================
--- lib/libc/gen/posix_spawn.c
+++ lib/libc/gen/posix_spawn.c
@@ -203,7 +203,7 @@
 	pid_t p;
 	volatile int error = 0;
 
-	p = vfork();
+	p = rfork(RFSPAWN);
 	switch (p) {
 	case -1:
 		return (errno);
Index: lib/libc/sys/rfork.2
===================================================================
--- lib/libc/sys/rfork.2
+++ lib/libc/sys/rfork.2
@@ -5,7 +5,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 12, 2011
+.Dd February 1, 2019
 .Dt RFORK 2
 .Os
 .Sh NAME
@@ -34,7 +34,9 @@
 The
 .Fa flags
 argument
-is the logical OR of some subset of:
+is either
+.Dv RFSPAWN
+or the logical OR of some subset of:
 .Bl -tag -width ".Dv RFLINUXTHPN"
 .It Dv RFPROC
 If set a new process is created; otherwise changes affect the
@@ -105,6 +107,14 @@
 or all processes sharing the table exit.
 .Pp
 If
+.Dv RFSPAWN
+is passed,
+.Nm
+will use
+.Xr vfork 2
+semantics but reset all signal actions in the child to default.
+.Pp
+If
 .Dv RFPROC
 is set, the
 value returned in the parent process
Index: sys/kern/kern_fork.c
===================================================================
--- sys/kern/kern_fork.c
+++ sys/kern/kern_fork.c
@@ -175,7 +175,11 @@
 
 	AUDIT_ARG_FFLAGS(uap->flags);
 	bzero(&fr, sizeof(fr));
-	fr.fr_flags = uap->flags;
+	if (uap->flags & RFSPAWN) {
+		fr.fr_flags = RFFDG | RFPROC | RFPPWAIT | RFMEM;
+		fr.fr_flags2 = FR2_SPAWN;
+	} else
+		fr.fr_flags = uap->flags;
 	fr.fr_pidp = &pid;
 	error = fork1(td, &fr);
 	if (error == 0) {
@@ -474,7 +478,8 @@
 	if (fr->fr_flags & RFSIGSHARE) {
 		p2->p_sigacts = sigacts_hold(p1->p_sigacts);
 	} else {
-		sigacts_copy(newsigacts, p1->p_sigacts);
+		if (!(fr->fr_flags2 & FR2_SPAWN))
+			sigacts_copy(newsigacts, p1->p_sigacts);
 		p2->p_sigacts = newsigacts;
 	}
 
Index: sys/sys/proc.h
===================================================================
--- sys/sys/proc.h
+++ sys/sys/proc.h
@@ -997,6 +997,8 @@
 	int 		*fr_pd_fd;
 	int 		fr_pd_flags;
 	struct filecaps	*fr_pd_fcaps;
+	int 		fr_flags2;
+#define	FR2_SPAWN	0x00001
 };
 
 /*
Index: sys/sys/unistd.h
===================================================================
--- sys/sys/unistd.h
+++ sys/sys/unistd.h
@@ -189,10 +189,11 @@
 #define	RFTSIGFLAGS(signum)	((signum) << RFTSIGSHIFT)
 #define	RFPROCDESC	(1<<28)	/* return a process descriptor */
 #define	RFPPWAIT	(1<<31)	/* parent sleeps until child exits (vfork) */
+#define	RFSPAWN		(1<<31) /* vfork(2) semantics, clear signals */
 #define	RFFLAGS		(RFFDG | RFPROC | RFMEM | RFNOWAIT | RFCFDG | \
     RFTHREAD | RFSIGSHARE | RFLINUXTHPN | RFSTOPPED | RFHIGHPID | RFTSIGZMB | \
-    RFPROCDESC | RFPPWAIT)
-#define	RFKERNELONLY	(RFSTOPPED | RFHIGHPID | RFPPWAIT | RFPROCDESC)
+    RFPROCDESC | RFSPAWN | RFPPWAIT)
+#define	RFKERNELONLY	(RFSTOPPED | RFHIGHPID | RFPROCDESC)
 
 #endif /* __BSD_VISIBLE */