diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index 819a964166f1..90515fb784c0 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_prot.c,v 1.82 2004/04/25 16:42:41 simonb Exp $	*/
+/*	$NetBSD: kern_prot.c,v 1.83 2004/05/02 12:36:55 pk Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1990, 1991, 1993
@@ -41,7 +41,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_prot.c,v 1.82 2004/04/25 16:42:41 simonb Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_prot.c,v 1.83 2004/05/02 12:36:55 pk Exp $");
 
 #include "opt_compat_43.h"
 
@@ -620,6 +620,7 @@ crget(void)
 
 	cr = pool_get(&cred_pool, PR_WAITOK);
 	memset(cr, 0, sizeof(*cr));
+	simple_lock_init(&cr->cr_lock);
 	cr->cr_ref = 1;
 	return (cr);
 }
@@ -631,8 +632,12 @@ crget(void)
 void
 crfree(struct ucred *cr)
 {
+	int n;
 
-	if (--cr->cr_ref == 0)
+	simple_lock(&cr->cr_lock);
+	n = --cr->cr_ref;
+	simple_unlock(&cr->cr_lock);
+	if (n == 0)
 		pool_put(&cred_pool, cr);
 }
 
@@ -655,13 +660,18 @@ struct ucred *
 crcopy(struct ucred *cr)
 {
 	struct ucred *newcr;
+	int n;
 
-	if (cr->cr_ref == 1)
+	simple_lock(&cr->cr_lock);
+	n = cr->cr_ref;
+	simple_unlock(&cr->cr_lock);
+	if (n == 1)
 		return (cr);
+
 	newcr = crget();
-	*newcr = *cr;
+	memcpy(&newcr->cr_startcopy, &cr->cr_startcopy,
+		sizeof(struct ucred) - offsetof(struct ucred, cr_startcopy));
 	crfree(cr);
-	newcr->cr_ref = 1;
 	return (newcr);
 }
 
@@ -674,8 +684,8 @@ crdup(const struct ucred *cr)
 	struct ucred *newcr;
 
 	newcr = crget();
-	*newcr = *cr;
-	newcr->cr_ref = 1;
+	memcpy(&newcr->cr_startcopy, &cr->cr_startcopy,
+		sizeof(struct ucred) - offsetof(struct ucred, cr_startcopy));
 	return (newcr);
 }
 
diff --git a/sys/sys/ucred.h b/sys/sys/ucred.h
index c4a197908f40..5e0b0ddeac92 100644
--- a/sys/sys/ucred.h
+++ b/sys/sys/ucred.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: ucred.h,v 1.18 2003/08/07 16:34:21 agc Exp $	*/
+/*	$NetBSD: ucred.h,v 1.19 2004/05/02 12:36:55 pk Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -34,6 +34,8 @@
 #ifndef _SYS_UCRED_H_
 #define	_SYS_UCRED_H_
 
+#include <sys/lock.h>
+
 /*
  * Credentials.
  */
@@ -48,7 +50,9 @@ struct uucred {
 };
 
 struct ucred {
+	struct simplelock cr_lock;		/* mutex for ref count */
 	u_int32_t	cr_ref;			/* reference count */
+#define cr_startcopy	cr_uid			/* for dup & copy */
 	uid_t		cr_uid;			/* effective user id */
 	gid_t		cr_gid;			/* effective group id */
 	u_int32_t	cr_ngroups;		/* number of groups */
@@ -59,7 +63,12 @@ struct ucred {
 #define FSCRED ((struct ucred *)-2)	/* filesystem credential */
 
 #ifdef _KERNEL
-#define	crhold(cr)	(cr)->cr_ref++
+static void __inline__ crhold(struct ucred *cr)
+{
+	simple_lock(&cr->cr_lock);
+	cr->cr_ref++;
+	simple_unlock(&cr->cr_lock);
+}
 
 /* flags that control when do_setres{u,g}id will do anything */
 #define	ID_E_EQ_E	0x001		/* effective equals effective */