From: mpi <mpi@openbsd.org>
Date: Tue, 23 Mar 2021 10:30:40 +0000 (+0000)
Subject: Make a child execute fork_return() only if PTRACE_FORK has been specified.
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=af8964917e47849e103b45f84b226601281e0495;p=openbsd

Make a child execute fork_return() only if PTRACE_FORK has been specified.

fork_return() does an additional check to send a SIGTRAP (for a debugger)
but this signal might overwrite the SIGSTOP generated by the parent doing
a PT_ATTACH before the child has a change to execute any instruction.

Prevent a race visible only on SP system with regress/sys/kern/ptrace2.

ok kettenis@
---

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 2c84a9abf52..9ae645f2ac2 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_fork.c,v 1.234 2021/02/15 09:35:59 mpi Exp $	*/
+/*	$OpenBSD: kern_fork.c,v 1.235 2021/03/23 10:30:40 mpi Exp $	*/
 /*	$NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $	*/
 
 /*
@@ -95,12 +95,15 @@ fork_return(void *arg)
 int
 sys_fork(struct proc *p, void *v, register_t *retval)
 {
+	void (*func)(void *) = child_return;
 	int flags;
 
 	flags = FORK_FORK;
-	if (p->p_p->ps_ptmask & PTRACE_FORK)
+	if (p->p_p->ps_ptmask & PTRACE_FORK) {
 		flags |= FORK_PTRACE;
-	return fork1(p, flags, fork_return, NULL, retval, NULL);
+		func = fork_return;
+	}
+	return fork1(p, flags, func, NULL, retval, NULL);
 }
 
 int