o Merge contents of struct pcred into struct ucred. Specifically, add the

  real uid, saved uid, real gid, and saved gid to ucred, as well as the
  pcred->pc_uidinfo, which was associated with the real uid, only rename
  it to cr_ruidinfo so as not to conflict with cr_uidinfo, which
  corresponds to the effective uid.
o Remove p_cred from struct proc; add p_ucred to struct proc, replacing
  original macro that pointed.
  p->p_ucred to p->p_cred->pc_ucred.
o Universally update code so that it makes use of ucred instead of pcred,
  p->p_ucred instead of p->p_pcred, cr_ruidinfo instead of p_uidinfo,
  cr_{r,sv}{u,g}id instead of p_*, etc.
o Remove pcred0 and its initialization from init_main.c; initialize
  cr_ruidinfo there.
o Restruction many credential modification chunks to always crdup while
  we figure out locking and optimizations; generally speaking, this
  means moving to a structure like this:
        newcred = crdup(oldcred);
        ...
        p->p_ucred = newcred;
        crfree(oldcred);
  It's not race-free, but better than nothing.  There are also races
  in sys_process.c, all inter-process authorization, fork, exec, and
  exit.
o Remove sigio->sio_ruid since sigio->sio_ucred now contains the ruid;
  remove comments indicating that the old arrangement was a problem.
o Restructure exec1() a little to use newcred/oldcred arrangement, and
  use improved uid management primitives.
o Clean up exit1() so as to do less work in credential cleanup due to
  pcred removal.
o Clean up fork1() so as to do less work in credential cleanup and
  allocation.
o Clean up ktrcanset() to take into account changes, and move to using
  suser_xxx() instead of performing a direct uid==0 comparision.
o Improve commenting in various kern_prot.c credential modification
  calls to better document current behavior.  In a couple of places,
  current behavior is a little questionable and we need to check
  POSIX.1 to make sure it's "right".  More commenting work still
  remains to be done.
o Update credential management calls, such as crfree(), to take into
  account new ruidinfo reference.
o Modify or add the following uid and gid helper routines:
      change_euid()
      change_egid()
      change_ruid()
      change_rgid()
      change_svuid()
      change_svgid()
  In each case, the call now acts on a credential not a process, and as
  such no longer requires more complicated process locking/etc.  They
  now assume the caller will do any necessary allocation of an
  exclusive credential reference.  Each is commented to document its
  reference requirements.
o CANSIGIO() is simplified to require only credentials, not processes
  and pcreds.
o Remove lots of (p_pcred==NULL) checks.
o Add an XXX to authorization code in nfs_lock.c, since it's
  questionable, and needs to be considered carefully.
o Simplify posix4 authorization code to require only credentials, not
  processes and pcreds.  Note that this authorization, as well as
  CANSIGIO(), needs to be updated to use the p_cansignal() and
  p_cansched() centralized authorization routines, as they currently
  do not take into account some desirable restrictions that are handled
  by the centralized routines, as well as being inconsistent with other
  similar authorization instances.
o Update libkvm to take these changes into account.

Obtained from:	TrustedBSD Project
Reviewed by:	green, bde, jhb, freebsd-arch, freebsd-audit

1 files changed, 271 insertions, 180 deletions

diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index f0b4ff8..fcef6d0 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -210,7 +210,7 @@ getuid(p, uap)
 	struct getuid_args *uap;
 {
 
-	p->p_retval[0] = p->p_cred->p_ruid;
+	p->p_retval[0] = p->p_ucred->cr_ruid;
 #if defined(COMPAT_43) || defined(COMPAT_SUNOS)
 	p->p_retval[1] = p->p_ucred->cr_uid;
 #endif
@@ -253,7 +253,7 @@ getgid(p, uap)
 	struct getgid_args *uap;
 {
 
-	p->p_retval[0] = p->p_cred->p_rgid;
+	p->p_retval[0] = p->p_ucred->cr_rgid;
 #if defined(COMPAT_43) || defined(COMPAT_SUNOS)
 	p->p_retval[1] = p->p_ucred->cr_groups[0];
 #endif
@@ -293,18 +293,18 @@ getgroups(p, uap)
 	struct proc *p;
 	register struct	getgroups_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register u_int ngrp;
+	struct ucred *cred = p->p_ucred;
+	u_int ngrp;
 	int error;
 
 	if ((ngrp = uap->gidsetsize) == 0) {
-		p->p_retval[0] = pc->pc_ucred->cr_ngroups;
+		p->p_retval[0] = cred->cr_ngroups;
 		return (0);
 	}
-	if (ngrp < pc->pc_ucred->cr_ngroups)
+	if (ngrp < cred->cr_ngroups)
 		return (EINVAL);
-	ngrp = pc->pc_ucred->cr_ngroups;
-	if ((error = copyout((caddr_t)pc->pc_ucred->cr_groups,
+	ngrp = cred->cr_ngroups;
+	if ((error = copyout((caddr_t)cred->cr_groups,
 	    (caddr_t)uap->gidset, ngrp * sizeof(gid_t))))
 		return (error);
 	p->p_retval[0] = ngrp;
@@ -427,10 +427,12 @@ setuid(p, uap)
 	struct proc *p;
 	struct setuid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register uid_t uid;
+	struct ucred *newcred, *oldcred;
+	uid_t uid;
 	int error;
 
+	uid = uap->uid;
+	oldcred = p->p_ucred;
 	/*
 	 * See if we have "permission" by POSIX 1003.1 rules.
 	 *
@@ -448,17 +450,17 @@ setuid(p, uap)
 	 *    change.  Determined by compile options.
 	 * 3: Change euid last. (after tests in #2 for "appropriate privs")
 	 */
-	uid = uap->uid;
-	if (uid != pc->p_ruid &&		/* allow setuid(getuid()) */
+	if (uid != oldcred->cr_ruid &&		/* allow setuid(getuid()) */
 #ifdef _POSIX_SAVED_IDS
-	    uid != pc->p_svuid &&		/* allow setuid(saved gid) */
+	    uid != oldcred->cr_svuid &&		/* allow setuid(saved gid) */
 #endif
 #ifdef POSIX_APPENDIX_B_4_2_2	/* Use BSD-compat clause from B.4.2.2 */
-	    uid != pc->pc_ucred->cr_uid &&	/* allow setuid(geteuid()) */
+	    uid != oldcred->cr_uid &&		/* allow setuid(geteuid()) */
 #endif
-	    (error = suser_xxx(0, p, PRISON_ROOT)))
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)))
 		return (error);
 
+	newcred = crdup(oldcred);
 #ifdef _POSIX_SAVED_IDS
 	/*
 	 * Do we have "appropriate privileges" (are we root or uid == euid)
@@ -466,16 +468,16 @@ setuid(p, uap)
 	 */
 	if (
 #ifdef POSIX_APPENDIX_B_4_2_2	/* Use the clause from B.4.2.2 */
-	    uid == pc->pc_ucred->cr_uid ||
+	    uid == oldcred->cr_uid ||
 #endif
-	    suser_xxx(0, p, PRISON_ROOT) == 0) /* we are using privs */
+	    suser_xxx(oldcred, NULL, PRISON_ROOT) == 0) /* we are using privs */
 #endif
 	{
 		/*
 		 * Set the real uid and transfer proc count to new user.
 		 */
-		if (uid != pc->p_ruid) {
-			change_ruid(p, uid);
+		if (uid != oldcred->cr_ruid) {
+			change_ruid(newcred, uid);
 			setsugid(p);
 		}
 		/*
@@ -485,8 +487,8 @@ setuid(p, uap)
 		 * the security of seteuid() depends on it.  B.4.2.2 says it
 		 * is important that we should do this.
 		 */
-		if (pc->p_svuid != uid) {
-			pc->p_svuid = uid;
+		if (uid != oldcred->cr_svuid) {
+			change_svuid(newcred, uid);
 			setsugid(p);
 		}
 	}
@@ -495,10 +497,12 @@ setuid(p, uap)
 	 * In all permitted cases, we are changing the euid.
 	 * Copy credentials so other references do not see our changes.
 	 */
-	if (pc->pc_ucred->cr_uid != uid) {
-		change_euid(p, uid);
+	if (uid != oldcred->cr_uid) {
+		change_euid(newcred, uid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -513,23 +517,27 @@ seteuid(p, uap)
 	struct proc *p;
 	struct seteuid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register uid_t euid;
+	struct ucred *newcred, *oldcred;
+	uid_t euid;
 	int error;
 
 	euid = uap->euid;
-	if (euid != pc->p_ruid &&		/* allow seteuid(getuid()) */
-	    euid != pc->p_svuid &&		/* allow seteuid(saved uid) */
-	    (error = suser_xxx(0, p, PRISON_ROOT)))
+	oldcred = p->p_ucred;
+	if (euid != oldcred->cr_ruid &&		/* allow seteuid(getuid()) */
+	    euid != oldcred->cr_svuid &&	/* allow seteuid(saved uid) */
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)))
 		return (error);
 	/*
 	 * Everything's okay, do it.  Copy credentials so other references do
 	 * not see our changes.
 	 */
-	if (pc->pc_ucred->cr_uid != euid) {
-		change_euid(p, euid);
+	newcred = crdup(oldcred);
+	if (oldcred->cr_uid != euid) {
+		change_euid(newcred, euid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -544,10 +552,12 @@ setgid(p, uap)
 	struct proc *p;
 	struct setgid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register gid_t gid;
+	struct ucred *newcred, *oldcred;
+	gid_t gid;
 	int error;
 
+	gid = uap->gid;
+	oldcred = p->p_ucred;
 	/*
 	 * See if we have "permission" by POSIX 1003.1 rules.
 	 *
@@ -559,17 +569,17 @@ setgid(p, uap)
 	 *
 	 * For notes on the logic here, see setuid() above.
 	 */
-	gid = uap->gid;
-	if (gid != pc->p_rgid &&		/* allow setgid(getgid()) */
+	if (gid != oldcred->cr_rgid &&		/* allow setgid(getgid()) */
 #ifdef _POSIX_SAVED_IDS
-	    gid != pc->p_svgid &&		/* allow setgid(saved gid) */
+	    gid != oldcred->cr_svgid &&		/* allow setgid(saved gid) */
 #endif
 #ifdef POSIX_APPENDIX_B_4_2_2	/* Use BSD-compat clause from B.4.2.2 */
-	    gid != pc->pc_ucred->cr_groups[0] && /* allow setgid(getegid()) */
+	    gid != oldcred->cr_groups[0] && /* allow setgid(getegid()) */
 #endif
-	    (error = suser_xxx(0, p, PRISON_ROOT)))
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)))
 		return (error);
 
+	newcred = crdup(oldcred);
 #ifdef _POSIX_SAVED_IDS
 	/*
 	 * Do we have "appropriate privileges" (are we root or gid == egid)
@@ -577,16 +587,16 @@ setgid(p, uap)
 	 */
 	if (
 #ifdef POSIX_APPENDIX_B_4_2_2	/* use the clause from B.4.2.2 */
-	    gid == pc->pc_ucred->cr_groups[0] ||
+	    gid == oldcred->cr_groups[0] ||
 #endif
-	    suser_xxx(0, p, PRISON_ROOT) == 0) /* we are using privs */
+	    suser_xxx(oldcred, NULL, PRISON_ROOT) == 0) /* we are using privs */
 #endif
 	{
 		/*
 		 * Set real gid
 		 */
-		if (pc->p_rgid != gid) {
-			pc->p_rgid = gid;
+		if (oldcred->cr_rgid != gid) {
+			change_rgid(newcred, gid);
 			setsugid(p);
 		}
 		/*
@@ -596,8 +606,8 @@ setgid(p, uap)
 		 * the security of setegid() depends on it.  B.4.2.2 says it
 		 * is important that we should do this.
 		 */
-		if (pc->p_svgid != gid) {
-			pc->p_svgid = gid;
+		if (oldcred->cr_svgid != gid) {
+			change_svgid(newcred, gid);
 			setsugid(p);
 		}
 	}
@@ -605,11 +615,12 @@ setgid(p, uap)
 	 * In all cases permitted cases, we are changing the egid.
 	 * Copy credentials so other references do not see our changes.
 	 */
-	if (pc->pc_ucred->cr_groups[0] != gid) {
-		pc->pc_ucred = crcopy(pc->pc_ucred);
-		pc->pc_ucred->cr_groups[0] = gid;
+	if (oldcred->cr_groups[0] != gid) {
+		change_egid(newcred, gid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -624,20 +635,23 @@ setegid(p, uap)
 	struct proc *p;
 	struct setegid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register gid_t egid;
+	struct ucred *newcred, *oldcred;
+	gid_t egid;
 	int error;
 
 	egid = uap->egid;
-	if (egid != pc->p_rgid &&		/* allow setegid(getgid()) */
-	    egid != pc->p_svgid &&		/* allow setegid(saved gid) */
-	    (error = suser_xxx(0, p, PRISON_ROOT)))
+	oldcred = p->p_ucred;
+	if (egid != oldcred->cr_rgid &&		/* allow setegid(getgid()) */
+	    egid != oldcred->cr_svgid &&	/* allow setegid(saved gid) */
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)))
 		return (error);
-	if (pc->pc_ucred->cr_groups[0] != egid) {
-		pc->pc_ucred = crcopy(pc->pc_ucred);
-		pc->pc_ucred->cr_groups[0] = egid;
+	newcred = crdup(oldcred);
+	if (oldcred->cr_groups[0] != egid) {
+		change_egid(newcred, egid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -653,20 +667,21 @@ setgroups(p, uap)
 	struct proc *p;
 	struct setgroups_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register u_int ngrp;
+	struct ucred *newcred, *oldcred;
+	u_int ngrp;
 	int error;
 
-	if ((error = suser_xxx(0, p, PRISON_ROOT)))
-		return (error);
 	ngrp = uap->gidsetsize;
+	oldcred = p->p_ucred;
+	if ((error = suser_xxx(oldcred, NULL, PRISON_ROOT)))
+		return (error);
 	if (ngrp > NGROUPS)
 		return (EINVAL);
 	/*
 	 * XXX A little bit lazy here.  We could test if anything has
 	 * changed before crcopy() and setting P_SUGID.
 	 */
-	pc->pc_ucred = crcopy(pc->pc_ucred);
+	newcred = crdup(oldcred);
 	if (ngrp < 1) {
 		/*
 		 * setgroups(0, NULL) is a legitimate way of clearing the
@@ -674,14 +689,18 @@ setgroups(p, uap)
 		 * have the egid in the groups[0]).  We risk security holes
 		 * when running non-BSD software if we do not do the same.
 		 */
-		pc->pc_ucred->cr_ngroups = 1;
+		newcred->cr_ngroups = 1;
 	} else {
 		if ((error = copyin((caddr_t)uap->gidset,
-		    (caddr_t)pc->pc_ucred->cr_groups, ngrp * sizeof(gid_t))))
+		    (caddr_t)newcred->cr_groups, ngrp * sizeof(gid_t)))) {
+			crfree(newcred);
 			return (error);
-		pc->pc_ucred->cr_ngroups = ngrp;
+		}
+		newcred->cr_ngroups = ngrp;
 	}
 	setsugid(p);
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -697,31 +716,35 @@ setreuid(p, uap)
 	register struct proc *p;
 	struct setreuid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register uid_t ruid, euid;
+	struct ucred *newcred, *oldcred;
+	uid_t ruid, euid;
 	int error;
 
 	ruid = uap->ruid;
 	euid = uap->euid;
-	if (((ruid != (uid_t)-1 && ruid != pc->p_ruid && ruid != pc->p_svuid) ||
-	     (euid != (uid_t)-1 && euid != pc->pc_ucred->cr_uid &&
-	     euid != pc->p_ruid && euid != pc->p_svuid)) &&
-	    (error = suser_xxx(0, p, PRISON_ROOT)) != 0)
+	oldcred = p->p_ucred;
+	if (((ruid != (uid_t)-1 && ruid != oldcred->cr_ruid &&
+	      ruid != oldcred->cr_svuid) ||
+	     (euid != (uid_t)-1 && euid != oldcred->cr_uid &&
+	      euid != oldcred->cr_ruid && euid != oldcred->cr_svuid)) &&
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)) != 0)
 		return (error);
-
-	if (euid != (uid_t)-1 && pc->pc_ucred->cr_uid != euid) {
-		change_euid(p, euid);
+	newcred = crdup(oldcred);
+	if (euid != (uid_t)-1 && oldcred->cr_uid != euid) {
+		change_euid(newcred, euid);
 		setsugid(p);
 	}
-	if (ruid != (uid_t)-1 && pc->p_ruid != ruid) {
-		change_ruid(p, ruid);
+	if (ruid != (uid_t)-1 && oldcred->cr_ruid != ruid) {
+		change_ruid(newcred, ruid);
 		setsugid(p);
 	}
-	if ((ruid != (uid_t)-1 || pc->pc_ucred->cr_uid != pc->p_ruid) &&
-	    pc->p_svuid != pc->pc_ucred->cr_uid) {
-		pc->p_svuid = pc->pc_ucred->cr_uid;
+	if ((ruid != (uid_t)-1 || newcred->cr_uid != newcred->cr_ruid) &&
+	    newcred->cr_svuid != newcred->cr_uid) {
+		change_svuid(newcred, newcred->cr_uid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -737,30 +760,32 @@ setregid(p, uap)
 	register struct proc *p;
 	struct setregid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register gid_t rgid, egid;
+	struct ucred *newcred, *oldcred;
+	gid_t rgid, egid;
 	int error;
 
 	rgid = uap->rgid;
 	egid = uap->egid;
-	if (((rgid != (gid_t)-1 && rgid != pc->p_rgid && rgid != pc->p_svgid) ||
-	     (egid != (gid_t)-1 && egid != pc->pc_ucred->cr_groups[0] &&
-	     egid != pc->p_rgid && egid != pc->p_svgid)) &&
-	    (error = suser_xxx(0, p, PRISON_ROOT)) != 0)
+	oldcred = p->p_ucred;
+	if (((rgid != (gid_t)-1 && rgid != oldcred->cr_rgid &&
+	    rgid != oldcred->cr_svgid) ||
+	     (egid != (gid_t)-1 && egid != oldcred->cr_groups[0] &&
+	     egid != oldcred->cr_rgid && egid != oldcred->cr_svgid)) &&
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)) != 0)
 		return (error);
 
-	if (egid != (gid_t)-1 && pc->pc_ucred->cr_groups[0] != egid) {
-		pc->pc_ucred = crcopy(pc->pc_ucred);
-		pc->pc_ucred->cr_groups[0] = egid;
+	newcred = crdup(oldcred);
+	if (egid != (gid_t)-1 && oldcred->cr_groups[0] != egid) {
+		change_egid(newcred, egid);
 		setsugid(p);
 	}
-	if (rgid != (gid_t)-1 && pc->p_rgid != rgid) {
-		pc->p_rgid = rgid;
+	if (rgid != (gid_t)-1 && oldcred->cr_rgid != rgid) {
+		change_rgid(newcred, rgid);
 		setsugid(p);
 	}
-	if ((rgid != (gid_t)-1 || pc->pc_ucred->cr_groups[0] != pc->p_rgid) &&
-	    pc->p_svgid != pc->pc_ucred->cr_groups[0]) {
-		pc->p_svgid = pc->pc_ucred->cr_groups[0];
+	if ((rgid != (gid_t)-1 || newcred->cr_groups[0] != newcred->cr_rgid) &&
+	    newcred->cr_svgid != newcred->cr_groups[0]) {
+		change_svgid(newcred, newcred->cr_groups[0]);
 		setsugid(p);
 	}
 	return (0);
@@ -784,33 +809,41 @@ setresuid(p, uap)
 	register struct proc *p;
 	struct setresuid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register uid_t ruid, euid, suid;
+	struct ucred *newcred, *oldcred;
+	uid_t ruid, euid, suid;
 	int error;
 
 	ruid = uap->ruid;
 	euid = uap->euid;
 	suid = uap->suid;
-	if (((ruid != (uid_t)-1 && ruid != pc->p_ruid && ruid != pc->p_svuid &&
-	      ruid != pc->pc_ucred->cr_uid) ||
-	     (euid != (uid_t)-1 && euid != pc->p_ruid && euid != pc->p_svuid &&
-	      euid != pc->pc_ucred->cr_uid) ||
-	     (suid != (uid_t)-1 && suid != pc->p_ruid && suid != pc->p_svuid &&
-	      suid != pc->pc_ucred->cr_uid)) &&
-	    (error = suser_xxx(0, p, PRISON_ROOT)) != 0)
+	oldcred = p->p_ucred;
+	if (((ruid != (uid_t)-1 && ruid != oldcred->cr_ruid &&
+	     ruid != oldcred->cr_svuid &&
+	      ruid != oldcred->cr_uid) ||
+	     (euid != (uid_t)-1 && euid != oldcred->cr_ruid &&
+	    euid != oldcred->cr_svuid &&
+	      euid != oldcred->cr_uid) ||
+	     (suid != (uid_t)-1 && suid != oldcred->cr_ruid &&
+	    suid != oldcred->cr_svuid &&
+	      suid != oldcred->cr_uid)) &&
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)) != 0)
 		return (error);
-	if (euid != (uid_t)-1 && pc->pc_ucred->cr_uid != euid) {
-		change_euid(p, euid);
+
+	newcred = crdup(oldcred);
+	if (euid != (uid_t)-1 && oldcred->cr_uid != euid) {
+		change_euid(newcred, euid);
 		setsugid(p);
 	}
-	if (ruid != (uid_t)-1 && pc->p_ruid != ruid) {
-		change_ruid(p, ruid);
+	if (ruid != (uid_t)-1 && oldcred->cr_ruid != ruid) {
+		change_ruid(newcred, ruid);
 		setsugid(p);
 	}
-	if (suid != (uid_t)-1 && pc->p_svuid != suid) {
-		pc->p_svuid = suid;
+	if (suid != (uid_t)-1 && oldcred->cr_svuid != suid) {
+		change_svuid(newcred, suid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -832,35 +865,41 @@ setresgid(p, uap)
 	register struct proc *p;
 	struct setresgid_args *uap;
 {
-	register struct pcred *pc = p->p_cred;
-	register gid_t rgid, egid, sgid;
+	struct ucred *newcred, *oldcred;
+	gid_t rgid, egid, sgid;
 	int error;
 
 	rgid = uap->rgid;
 	egid = uap->egid;
 	sgid = uap->sgid;
-	if (((rgid != (gid_t)-1 && rgid != pc->p_rgid && rgid != pc->p_svgid &&
-	      rgid != pc->pc_ucred->cr_groups[0]) ||
-	     (egid != (gid_t)-1 && egid != pc->p_rgid && egid != pc->p_svgid &&
-	      egid != pc->pc_ucred->cr_groups[0]) ||
-	     (sgid != (gid_t)-1 && sgid != pc->p_rgid && sgid != pc->p_svgid &&
-	      sgid != pc->pc_ucred->cr_groups[0])) &&
-	    (error = suser_xxx(0, p, PRISON_ROOT)) != 0)
+	oldcred = p->p_ucred;
+	if (((rgid != (gid_t)-1 && rgid != oldcred->cr_rgid &&
+	      rgid != oldcred->cr_svgid &&
+	      rgid != oldcred->cr_groups[0]) ||
+	     (egid != (gid_t)-1 && egid != oldcred->cr_rgid &&
+	      egid != oldcred->cr_svgid &&
+	      egid != oldcred->cr_groups[0]) ||
+	     (sgid != (gid_t)-1 && sgid != oldcred->cr_rgid &&
+	      sgid != oldcred->cr_svgid &&
+	      sgid != oldcred->cr_groups[0])) &&
+	    (error = suser_xxx(oldcred, NULL, PRISON_ROOT)) != 0)
 		return (error);
 
-	if (egid != (gid_t)-1 && pc->pc_ucred->cr_groups[0] != egid) {
-		pc->pc_ucred = crcopy(pc->pc_ucred);
-		pc->pc_ucred->cr_groups[0] = egid;
+	newcred = crdup(oldcred);
+	if (egid != (gid_t)-1 && oldcred->cr_groups[0] != egid) {
+		change_egid(newcred, egid);
 		setsugid(p);
 	}
-	if (rgid != (gid_t)-1 && pc->p_rgid != rgid) {
-		pc->p_rgid = rgid;
+	if (rgid != (gid_t)-1 && oldcred->cr_rgid != rgid) {
+		change_rgid(newcred, rgid);
 		setsugid(p);
 	}
-	if (sgid != (gid_t)-1 && pc->p_svgid != sgid) {
-		pc->p_svgid = sgid;
+	if (sgid != (gid_t)-1 && oldcred->cr_svgid != sgid) {
+		change_svgid(newcred, sgid);
 		setsugid(p);
 	}
+	p->p_ucred = newcred;
+	crfree(oldcred);
 	return (0);
 }
 
@@ -877,18 +916,18 @@ getresuid(p, uap)
 	register struct proc *p;
 	struct getresuid_args *uap;
 {
-	struct pcred *pc = p->p_cred;
+	struct ucred *cred = p->p_ucred;
 	int error1 = 0, error2 = 0, error3 = 0;
 
 	if (uap->ruid)
-		error1 = copyout((caddr_t)&pc->p_ruid,
-		    (caddr_t)uap->ruid, sizeof(pc->p_ruid));
+		error1 = copyout((caddr_t)&cred->cr_ruid,
+		    (caddr_t)uap->ruid, sizeof(cred->cr_ruid));
 	if (uap->euid)
-		error2 = copyout((caddr_t)&pc->pc_ucred->cr_uid,
-		    (caddr_t)uap->euid, sizeof(pc->pc_ucred->cr_uid));
+		error2 = copyout((caddr_t)&cred->cr_uid,
+		    (caddr_t)uap->euid, sizeof(cred->cr_uid));
 	if (uap->suid)
-		error3 = copyout((caddr_t)&pc->p_svuid,
-		    (caddr_t)uap->suid, sizeof(pc->p_svuid));
+		error3 = copyout((caddr_t)&cred->cr_svuid,
+		    (caddr_t)uap->suid, sizeof(cred->cr_svuid));
 	return error1 ? error1 : (error2 ? error2 : error3);
 }
 
@@ -905,18 +944,18 @@ getresgid(p, uap)
 	register struct proc *p;
 	struct getresgid_args *uap;
 {
-	struct pcred *pc = p->p_cred;
+	struct ucred *cred = p->p_ucred;
 	int error1 = 0, error2 = 0, error3 = 0;
 
 	if (uap->rgid)
-		error1 = copyout((caddr_t)&pc->p_rgid,
-		    (caddr_t)uap->rgid, sizeof(pc->p_rgid));
+		error1 = copyout((caddr_t)&cred->cr_rgid,
+		    (caddr_t)uap->rgid, sizeof(cred->cr_rgid));
 	if (uap->egid)
-		error2 = copyout((caddr_t)&pc->pc_ucred->cr_groups[0],
-		    (caddr_t)uap->egid, sizeof(pc->pc_ucred->cr_groups[0]));
+		error2 = copyout((caddr_t)&cred->cr_groups[0],
+		    (caddr_t)uap->egid, sizeof(cred->cr_groups[0]));
 	if (uap->sgid)
-		error3 = copyout((caddr_t)&pc->p_svgid,
-		    (caddr_t)uap->sgid, sizeof(pc->p_svgid));
+		error3 = copyout((caddr_t)&cred->cr_svgid,
+		    (caddr_t)uap->sgid, sizeof(cred->cr_svgid));
 	return error1 ? error1 : (error2 ? error2 : error3);
 }
 
@@ -972,7 +1011,7 @@ __setugid(p, uap)
 int
 groupmember(gid, cred)
 	gid_t gid;
-	register struct ucred *cred;
+	struct ucred *cred;
 {
 	register gid_t *gp;
 	gid_t *egp;
@@ -1038,7 +1077,7 @@ u_cansee(struct ucred *u1, struct ucred *u2)
 
 	if ((error = prison_check(u1, u2)))
 		return (error);
-	if (!ps_showallprocs && u1->cr_uid != u2->cr_uid) {
+	if (!ps_showallprocs && u1->cr_ruid != u2->cr_ruid) {
 		if (suser_xxx(u1, NULL, PRISON_ROOT) != 0)
 			return (ESRCH);
 	}
@@ -1113,10 +1152,10 @@ p_cansignal(struct proc *p1, struct proc *p2, int signum)
 	 * Generally, the object credential's ruid or svuid must match the
 	 * subject credential's ruid or euid.
 	 */
-	if (p1->p_cred->p_ruid != p2->p_cred->p_ruid &&
-	    p1->p_cred->p_ruid != p2->p_cred->p_svuid &&
-	    p1->p_ucred->cr_uid != p2->p_cred->p_ruid &&
-	    p1->p_ucred->cr_uid != p2->p_cred->p_svuid) {
+	if (p1->p_ucred->cr_ruid != p2->p_ucred->cr_ruid &&
+	    p1->p_ucred->cr_ruid != p2->p_ucred->cr_svuid &&
+	    p1->p_ucred->cr_uid != p2->p_ucred->cr_ruid &&
+	    p1->p_ucred->cr_uid != p2->p_ucred->cr_svuid) {
 		/* Not permitted, try privilege. */
 		error = suser_xxx(NULL, p1, PRISON_ROOT);
 		if (error)
@@ -1140,9 +1179,9 @@ p_cansched(struct proc *p1, struct proc *p2, int *privused)
 	if ((error = prison_check(p1->p_ucred, p2->p_ucred)))
 		return (error);
 
-	if (p1->p_cred->p_ruid == p2->p_cred->p_ruid)
+	if (p1->p_ucred->cr_ruid == p2->p_ucred->cr_ruid)
 		return (0);
-	if (p1->p_ucred->cr_uid == p2->p_cred->p_ruid)
+	if (p1->p_ucred->cr_uid == p2->p_ucred->cr_ruid)
 		return (0);
 
 	if (!suser_xxx(0, p1, PRISON_ROOT)) {
@@ -1178,9 +1217,9 @@ p_candebug(struct proc *p1, struct proc *p2, int *privused)
 
 	/* not owned by you, has done setuid (unless you're root) */
 	/* add a CAP_SYS_PTRACE here? */
-	if (p1->p_cred->pc_ucred->cr_uid != p2->p_cred->pc_ucred->cr_uid ||
-	    p1->p_cred->pc_ucred->cr_uid != p2->p_cred->p_svuid ||
-	    p1->p_cred->pc_ucred->cr_uid != p2->p_cred->p_ruid ||
+	if (p1->p_ucred->cr_uid != p2->p_ucred->cr_uid ||
+	    p1->p_ucred->cr_uid != p2->p_ucred->cr_svuid ||
+	    p1->p_ucred->cr_uid != p2->p_ucred->cr_ruid ||
 	    p2->p_flag & P_SUGID) {
 		if ((error = suser_xxx(0, p1, PRISON_ROOT)))
 			return (error);
@@ -1308,6 +1347,7 @@ crdup(cr)
 	*newcr = *cr;
 	mtx_init(&newcr->cr_mtx, "ucred", MTX_DEF);
 	uihold(newcr->cr_uidinfo);
+	uihold(newcr->cr_ruidinfo);
 	if (jailed(newcr))
 		prison_hold(newcr->cr_prison);
 	newcr->cr_ref = 1;
@@ -1375,48 +1415,99 @@ setsugid(p)
 }
 
 /*
- * Helper function to change the effective uid of a process
+ * change_euid(): Change a process's effective uid.
+ * Side effects: newcred->cr_uid and newcred->cr_uidinfo will be modified.
+ * References: newcred must be an exclusive credential reference for the
+ *             duration of the call.
  */
 void
-change_euid(p, euid)
-	struct	proc *p;
-	uid_t	euid;
+change_euid(newcred, euid)
+	struct ucred *newcred;
+	uid_t euid;
 {
-	struct	pcred *pc;
-	struct	uidinfo *uip;
 
-	pc = p->p_cred;
-	/*
-	 * crcopy is essentially a NOP if ucred has a reference count
-	 * of 1, which is true if it has already been copied.
-	 */
-	pc->pc_ucred = crcopy(pc->pc_ucred);
-	uip = pc->pc_ucred->cr_uidinfo;
-	pc->pc_ucred->cr_uid = euid;
-	pc->pc_ucred->cr_uidinfo = uifind(euid);
-	uifree(uip);
+	newcred->cr_uid = euid;
+	uifree(newcred->cr_uidinfo);
+	newcred->cr_uidinfo = uifind(euid);
 }
 
 /*
- * Helper function to change the real uid of a process
- *
- * The per-uid process count for this process is transfered from
- * the old uid to the new uid.
+ * change_egid(): Change a process's effective gid.
+ * Side effects: newcred->cr_gid will be modified.
+ * References: newcred must be an exclusive credential reference for the
+ *             duration of the call.
  */
 void
-change_ruid(p, ruid)
-	struct	proc *p;
-	uid_t	ruid;
+change_egid(newcred, egid)
+	struct ucred *newcred;
+	gid_t egid;
+{
+
+	newcred->cr_groups[0] = egid;
+}
+
+/*
+ * change_ruid(): Change a process's real uid.
+ * Side effects: newcred->cr_ruid will be updated, newcred->cr_ruidinfo
+ *               will be updated, and the old and new cr_ruidinfo proc
+ *               counts will be updated.
+ * References: newcred must be an exclusive credential reference for the
+ *             duration of the call.
+ */
+void
+change_ruid(newcred, ruid)
+	struct ucred *newcred;
+	uid_t ruid;
+{
+
+	(void)chgproccnt(newcred->cr_ruidinfo, -1, 0);
+	newcred->cr_ruid = ruid;
+	uifree(newcred->cr_ruidinfo);
+	newcred->cr_ruidinfo = uifind(ruid);
+	(void)chgproccnt(newcred->cr_ruidinfo, 1, 0);
+}
+
+/*
+ * change_rgid(): Change a process's real gid.
+ * Side effects: newcred->cr_rgid will be updated.
+ * References: newcred must be an exclusive credential reference for the
+ *             duration of the call.
+ */
+void
+change_rgid(newcred, rgid)
+	struct ucred *newcred;
+	gid_t rgid;
 {
-	struct	pcred *pc;
-	struct	uidinfo *uip;
-
-	pc = p->p_cred;
-	(void)chgproccnt(pc->p_uidinfo, -1, 0);
-	uip = pc->p_uidinfo;
-	/* It is assumed that pcred is not shared between processes */
-	pc->p_ruid = ruid;
-	pc->p_uidinfo = uifind(ruid);
-	(void)chgproccnt(pc->p_uidinfo, 1, 0);
-	uifree(uip);
+
+	newcred->cr_rgid = rgid;
+}
+
+/*
+ * change_svuid(): Change a process's saved uid.
+ * Side effects: newcred->cr_svuid will be updated.
+ * References: newcred must be an exclusive credential reference for the
+ *             duration of the call.
+ */
+void
+change_svuid(newcred, svuid)
+	struct ucred *newcred;
+	uid_t svuid;
+{
+
+	newcred->cr_svuid = svuid;
+}
+
+/*
+ * change_svgid(): Change a process's saved gid.
+ * Side effects: newcred->cr_svgid will be updated.
+ * References: newcred must be an exclusive credential reference for the
+ *             duration of the call.
+ */
+void
+change_svgid(newcred, svgid)
+	struct ucred *newcred;
+	gid_t svgid;
+{
+
+	newcred->cr_svgid = svgid;
 }