Ignore machine-check MSRs

[freebsd-src/fkvm-freebsd.git] / sys / kern / kern_prot.c

/*-
 * Copyright (c) 1982, 1986, 1989, 1990, 1991, 1993
 *      The Regents of the University of California.
 * (c) UNIX System Laboratories, Inc.
 * Copyright (c) 2000-2001 Robert N. M. Watson.
 * All rights reserved.
 *
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)kern_prot.c 8.6 (Berkeley) 1/21/94
 */

/*
 * System calls related to processes and protection
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_compat.h"
#include "opt_mac.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/acct.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/refcount.h>
#include <sys/sx.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/sysproto.h>
#include <sys/jail.h>
#include <sys/pioctl.h>
#include <sys/resourcevar.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/syscallsubr.h>
#include <sys/sysctl.h>

#include <security/audit/audit.h>
#include <security/mac/mac_framework.h>

static MALLOC_DEFINE(M_CRED, "cred", "credentials");

SYSCTL_NODE(_security, OID_AUTO, bsd, CTLFLAG_RW, 0, "BSD security policy");

#ifndef _SYS_SYSPROTO_H_
struct getpid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
getpid(struct thread *td, struct getpid_args *uap)
{
        struct proc *p = td->td_proc;

        td->td_retval[0] = p->p_pid;
#if defined(COMPAT_43)
        PROC_LOCK(p);
        td->td_retval[1] = p->p_pptr->p_pid;
        PROC_UNLOCK(p);
#endif
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct getppid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
getppid(struct thread *td, struct getppid_args *uap)
{
        struct proc *p = td->td_proc;

        PROC_LOCK(p);
        td->td_retval[0] = p->p_pptr->p_pid;
        PROC_UNLOCK(p);
        return (0);
}

/*
 * Get process group ID; note that POSIX getpgrp takes no parameter.
 */
#ifndef _SYS_SYSPROTO_H_
struct getpgrp_args {
        int     dummy;
};
#endif
int
getpgrp(struct thread *td, struct getpgrp_args *uap)
{
        struct proc *p = td->td_proc;

        PROC_LOCK(p);
        td->td_retval[0] = p->p_pgrp->pg_id;
        PROC_UNLOCK(p);
        return (0);
}

/* Get an arbitary pid's process group id */
#ifndef _SYS_SYSPROTO_H_
struct getpgid_args {
        pid_t   pid;
};
#endif
int
getpgid(struct thread *td, struct getpgid_args *uap)
{
        struct proc *p;
        int error;

        if (uap->pid == 0) {
                p = td->td_proc;
                PROC_LOCK(p);
        } else {
                p = pfind(uap->pid);
                if (p == NULL)
                        return (ESRCH);
                error = p_cansee(td, p);
                if (error) {
                        PROC_UNLOCK(p);
                        return (error);
                }
        }
        td->td_retval[0] = p->p_pgrp->pg_id;
        PROC_UNLOCK(p);
        return (0);
}

/*
 * Get an arbitary pid's session id.
 */
#ifndef _SYS_SYSPROTO_H_
struct getsid_args {
        pid_t   pid;
};
#endif
int
getsid(struct thread *td, struct getsid_args *uap)
{
        struct proc *p;
        int error;

        if (uap->pid == 0) {
                p = td->td_proc;
                PROC_LOCK(p);
        } else {
                p = pfind(uap->pid);
                if (p == NULL)
                        return (ESRCH);
                error = p_cansee(td, p);
                if (error) {
                        PROC_UNLOCK(p);
                        return (error);
                }
        }
        td->td_retval[0] = p->p_session->s_sid;
        PROC_UNLOCK(p);
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct getuid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
getuid(struct thread *td, struct getuid_args *uap)
{

        td->td_retval[0] = td->td_ucred->cr_ruid;
#if defined(COMPAT_43)
        td->td_retval[1] = td->td_ucred->cr_uid;
#endif
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct geteuid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
geteuid(struct thread *td, struct geteuid_args *uap)
{

        td->td_retval[0] = td->td_ucred->cr_uid;
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct getgid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
getgid(struct thread *td, struct getgid_args *uap)
{

        td->td_retval[0] = td->td_ucred->cr_rgid;
#if defined(COMPAT_43)
        td->td_retval[1] = td->td_ucred->cr_groups[0];
#endif
        return (0);
}

/*
 * Get effective group ID.  The "egid" is groups[0], and could be obtained
 * via getgroups.  This syscall exists because it is somewhat painful to do
 * correctly in a library function.
 */
#ifndef _SYS_SYSPROTO_H_
struct getegid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
getegid(struct thread *td, struct getegid_args *uap)
{

        td->td_retval[0] = td->td_ucred->cr_groups[0];
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct getgroups_args {
        u_int   gidsetsize;
        gid_t   *gidset;
};
#endif
int
getgroups(struct thread *td, register struct getgroups_args *uap)
{
        gid_t groups[NGROUPS];
        u_int ngrp;
        int error;

        ngrp = MIN(uap->gidsetsize, NGROUPS);
        error = kern_getgroups(td, &ngrp, groups);
        if (error)
                return (error);
        if (uap->gidsetsize > 0)
                error = copyout(groups, uap->gidset, ngrp * sizeof(gid_t));
        if (error == 0)
                td->td_retval[0] = ngrp;
        return (error);
}

int
kern_getgroups(struct thread *td, u_int *ngrp, gid_t *groups)
{
        struct ucred *cred;

        cred = td->td_ucred;
        if (*ngrp == 0) {
                *ngrp = cred->cr_ngroups;
                return (0);
        }
        if (*ngrp < cred->cr_ngroups)
                return (EINVAL);
        *ngrp = cred->cr_ngroups;
        bcopy(cred->cr_groups, groups, *ngrp * sizeof(gid_t));
        return (0);
}

#ifndef _SYS_SYSPROTO_H_
struct setsid_args {
        int     dummy;
};
#endif
/* ARGSUSED */
int
setsid(register struct thread *td, struct setsid_args *uap)
{
        struct pgrp *pgrp;
        int error;
        struct proc *p = td->td_proc;
        struct pgrp *newpgrp;
        struct session *newsess;

        error = 0;
        pgrp = NULL;

        MALLOC(newpgrp, struct pgrp *, sizeof(struct pgrp), M_PGRP, M_WAITOK | M_ZERO);
        MALLOC(newsess, struct session *, sizeof(struct session), M_SESSION, M_WAITOK | M_ZERO);

        sx_xlock(&proctree_lock);

        if (p->p_pgid == p->p_pid || (pgrp = pgfind(p->p_pid)) != NULL) {
                if (pgrp != NULL)
                        PGRP_UNLOCK(pgrp);
                error = EPERM;
        } else {
                (void)enterpgrp(p, p->p_pid, newpgrp, newsess);
                td->td_retval[0] = p->p_pid;
                newpgrp = NULL;
                newsess = NULL;
        }

        sx_xunlock(&proctree_lock);

        if (newpgrp != NULL)
                FREE(newpgrp, M_PGRP);
        if (newsess != NULL)
                FREE(newsess, M_SESSION);

        return (error);
}

/*
 * set process group (setpgid/old setpgrp)
 *
 * caller does setpgid(targpid, targpgid)
 *
 * pid must be caller or child of caller (ESRCH)
 * if a child
 *      pid must be in same session (EPERM)
 *      pid can't have done an exec (EACCES)
 * if pgid != pid
 *      there must exist some pid in same session having pgid (EPERM)
 * pid must not be session leader (EPERM)
 */
#ifndef _SYS_SYSPROTO_H_
struct setpgid_args {
        int     pid;            /* target process id */
        int     pgid;           /* target pgrp id */
};
#endif
/* ARGSUSED */
int
setpgid(struct thread *td, register struct setpgid_args *uap)
{
        struct proc *curp = td->td_proc;
        register struct proc *targp;    /* target process */
        register struct pgrp *pgrp;     /* target pgrp */
        int error;
        struct pgrp *newpgrp;

        if (uap->pgid < 0)
                return (EINVAL);

        error = 0;

        MALLOC(newpgrp, struct pgrp *, sizeof(struct pgrp), M_PGRP, M_WAITOK | M_ZERO);

        sx_xlock(&proctree_lock);
        if (uap->pid != 0 && uap->pid != curp->p_pid) {
                if ((targp = pfind(uap->pid)) == NULL) {
                        error = ESRCH;
                        goto done;
                }
                if (!inferior(targp)) {
                        PROC_UNLOCK(targp);
                        error = ESRCH;
                        goto done;
                }
                if ((error = p_cansee(td, targp))) {
                        PROC_UNLOCK(targp);
                        goto done;
                }
                if (targp->p_pgrp == NULL ||
                    targp->p_session != curp->p_session) {
                        PROC_UNLOCK(targp);
                        error = EPERM;
                        goto done;
                }
                if (targp->p_flag & P_EXEC) {
                        PROC_UNLOCK(targp);
                        error = EACCES;
                        goto done;
                }
                PROC_UNLOCK(targp);
        } else
                targp = curp;
        if (SESS_LEADER(targp)) {
                error = EPERM;
                goto done;
        }
        if (uap->pgid == 0)
                uap->pgid = targp->p_pid;
        if ((pgrp = pgfind(uap->pgid)) == NULL) {
                if (uap->pgid == targp->p_pid) {
                        error = enterpgrp(targp, uap->pgid, newpgrp,
                            NULL);
                        if (error == 0)
                                newpgrp = NULL;
                } else
                        error = EPERM;
        } else {
                if (pgrp == targp->p_pgrp) {
                        PGRP_UNLOCK(pgrp);
                        goto done;
                }
                if (pgrp->pg_id != targp->p_pid &&
                    pgrp->pg_session != curp->p_session) {
                        PGRP_UNLOCK(pgrp);
                        error = EPERM;
                        goto done;
                }
                PGRP_UNLOCK(pgrp);
                error = enterthispgrp(targp, pgrp);
        }
done:
        sx_xunlock(&proctree_lock);
        KASSERT((error == 0) || (newpgrp != NULL),
            ("setpgid failed and newpgrp is NULL"));
        if (newpgrp != NULL)
                FREE(newpgrp, M_PGRP);
        return (error);
}

/*
 * Use the clause in B.4.2.2 that allows setuid/setgid to be 4.2/4.3BSD
 * compatible.  It says that setting the uid/gid to euid/egid is a special
 * case of "appropriate privilege".  Once the rules are expanded out, this
 * basically means that setuid(nnn) sets all three id's, in all permitted
 * cases unless _POSIX_SAVED_IDS is enabled.  In that case, setuid(getuid())
 * does not set the saved id - this is dangerous for traditional BSD
 * programs.  For this reason, we *really* do not want to set
 * _POSIX_SAVED_IDS and do not want to clear POSIX_APPENDIX_B_4_2_2.
 */
#define POSIX_APPENDIX_B_4_2_2

#ifndef _SYS_SYSPROTO_H_
struct setuid_args {
        uid_t   uid;
};
#endif
/* ARGSUSED */
int
setuid(struct thread *td, struct setuid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        uid_t uid;
        struct uidinfo *uip;
        int error;

        uid = uap->uid;
        AUDIT_ARG(uid, uid);
        newcred = crget();
        uip = uifind(uid);
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setuid(p, oldcred, uid);
        if (error)
                goto fail;
#endif

        /*
         * See if we have "permission" by POSIX 1003.1 rules.
         *
         * Note that setuid(geteuid()) is a special case of
         * "appropriate privileges" in appendix B.4.2.2.  We need
         * to use this clause to be compatible with traditional BSD
         * semantics.  Basically, it means that "setuid(xx)" sets all
         * three id's (assuming you have privs).
         *
         * Notes on the logic.  We do things in three steps.
         * 1: We determine if the euid is going to change, and do EPERM
         *    right away.  We unconditionally change the euid later if this
         *    test is satisfied, simplifying that part of the logic.
         * 2: We determine if the real and/or saved uids are going to
         *    change.  Determined by compile options.
         * 3: Change euid last. (after tests in #2 for "appropriate privs")
         */
        if (uid != oldcred->cr_ruid &&          /* allow setuid(getuid()) */
#ifdef _POSIX_SAVED_IDS
            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 != oldcred->cr_uid &&           /* allow setuid(geteuid()) */
#endif
            (error = priv_check_cred(oldcred, PRIV_CRED_SETUID, 0)) != 0)
                goto fail;

        /*
         * Copy credentials so other references do not see our changes.
         */
        crcopy(newcred, oldcred);
#ifdef _POSIX_SAVED_IDS
        /*
         * Do we have "appropriate privileges" (are we root or uid == euid)
         * If so, we are changing the real uid and/or saved uid.
         */
        if (
#ifdef POSIX_APPENDIX_B_4_2_2   /* Use the clause from B.4.2.2 */
            uid == oldcred->cr_uid ||
#endif
            /* We are using privs. */
            priv_check_cred(oldcred, PRIV_CRED_SETUID, 0) == 0)
#endif
        {
                /*
                 * Set the real uid and transfer proc count to new user.
                 */
                if (uid != oldcred->cr_ruid) {
                        change_ruid(newcred, uip);
                        setsugid(p);
                }
                /*
                 * Set saved uid
                 *
                 * XXX always set saved uid even if not _POSIX_SAVED_IDS, as
                 * the security of seteuid() depends on it.  B.4.2.2 says it
                 * is important that we should do this.
                 */
                if (uid != oldcred->cr_svuid) {
                        change_svuid(newcred, uid);
                        setsugid(p);
                }
        }

        /*
         * In all permitted cases, we are changing the euid.
         */
        if (uid != oldcred->cr_uid) {
                change_euid(newcred, uip);
                setsugid(p);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        uifree(uip);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        uifree(uip);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct seteuid_args {
        uid_t   euid;
};
#endif
/* ARGSUSED */
int
seteuid(struct thread *td, struct seteuid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        uid_t euid;
        struct uidinfo *euip;
        int error;

        euid = uap->euid;
        AUDIT_ARG(euid, euid);
        newcred = crget();
        euip = uifind(euid);
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_seteuid(p, oldcred, euid);
        if (error)
                goto fail;
#endif

        if (euid != oldcred->cr_ruid &&         /* allow seteuid(getuid()) */
            euid != oldcred->cr_svuid &&        /* allow seteuid(saved uid) */
            (error = priv_check_cred(oldcred, PRIV_CRED_SETEUID, 0)) != 0)
                goto fail;

        /*
         * Everything's okay, do it.  Copy credentials so other references do
         * not see our changes.
         */
        crcopy(newcred, oldcred);
        if (oldcred->cr_uid != euid) {
                change_euid(newcred, euip);
                setsugid(p);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        uifree(euip);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        uifree(euip);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct setgid_args {
        gid_t   gid;
};
#endif
/* ARGSUSED */
int
setgid(struct thread *td, struct setgid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        gid_t gid;
        int error;

        gid = uap->gid;
        AUDIT_ARG(gid, gid);
        newcred = crget();
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setgid(p, oldcred, gid);
        if (error)
                goto fail;
#endif

        /*
         * See if we have "permission" by POSIX 1003.1 rules.
         *
         * Note that setgid(getegid()) is a special case of
         * "appropriate privileges" in appendix B.4.2.2.  We need
         * to use this clause to be compatible with traditional BSD
         * semantics.  Basically, it means that "setgid(xx)" sets all
         * three id's (assuming you have privs).
         *
         * For notes on the logic here, see setuid() above.
         */
        if (gid != oldcred->cr_rgid &&          /* allow setgid(getgid()) */
#ifdef _POSIX_SAVED_IDS
            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 != oldcred->cr_groups[0] && /* allow setgid(getegid()) */
#endif
            (error = priv_check_cred(oldcred, PRIV_CRED_SETGID, 0)) != 0)
                goto fail;

        crcopy(newcred, oldcred);
#ifdef _POSIX_SAVED_IDS
        /*
         * Do we have "appropriate privileges" (are we root or gid == egid)
         * If so, we are changing the real uid and saved gid.
         */
        if (
#ifdef POSIX_APPENDIX_B_4_2_2   /* use the clause from B.4.2.2 */
            gid == oldcred->cr_groups[0] ||
#endif
            /* We are using privs. */
            priv_check_cred(oldcred, PRIV_CRED_SETGID, 0) == 0)
#endif
        {
                /*
                 * Set real gid
                 */
                if (oldcred->cr_rgid != gid) {
                        change_rgid(newcred, gid);
                        setsugid(p);
                }
                /*
                 * Set saved gid
                 *
                 * XXX always set saved gid even if not _POSIX_SAVED_IDS, as
                 * the security of setegid() depends on it.  B.4.2.2 says it
                 * is important that we should do this.
                 */
                if (oldcred->cr_svgid != gid) {
                        change_svgid(newcred, gid);
                        setsugid(p);
                }
        }
        /*
         * In all cases permitted cases, we are changing the egid.
         * Copy credentials so other references do not see our changes.
         */
        if (oldcred->cr_groups[0] != gid) {
                change_egid(newcred, gid);
                setsugid(p);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct setegid_args {
        gid_t   egid;
};
#endif
/* ARGSUSED */
int
setegid(struct thread *td, struct setegid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        gid_t egid;
        int error;

        egid = uap->egid;
        AUDIT_ARG(egid, egid);
        newcred = crget();
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setegid(p, oldcred, egid);
        if (error)
                goto fail;
#endif

        if (egid != oldcred->cr_rgid &&         /* allow setegid(getgid()) */
            egid != oldcred->cr_svgid &&        /* allow setegid(saved gid) */
            (error = priv_check_cred(oldcred, PRIV_CRED_SETEGID, 0)) != 0)
                goto fail;

        crcopy(newcred, oldcred);
        if (oldcred->cr_groups[0] != egid) {
                change_egid(newcred, egid);
                setsugid(p);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct setgroups_args {
        u_int   gidsetsize;
        gid_t   *gidset;
};
#endif
/* ARGSUSED */
int
setgroups(struct thread *td, struct setgroups_args *uap)
{
        gid_t groups[NGROUPS];
        int error;

        if (uap->gidsetsize > NGROUPS)
                return (EINVAL);
        error = copyin(uap->gidset, groups, uap->gidsetsize * sizeof(gid_t));
        if (error)
                return (error);
        return (kern_setgroups(td, uap->gidsetsize, groups));
}

int
kern_setgroups(struct thread *td, u_int ngrp, gid_t *groups)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        int error;

        if (ngrp > NGROUPS)
                return (EINVAL);
        AUDIT_ARG(groupset, groups, ngrp);
        newcred = crget();
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setgroups(p, oldcred, ngrp, groups);
        if (error)
                goto fail;
#endif

        error = priv_check_cred(oldcred, PRIV_CRED_SETGROUPS, 0);
        if (error)
                goto fail;

        /*
         * XXX A little bit lazy here.  We could test if anything has
         * changed before crcopy() and setting P_SUGID.
         */
        crcopy(newcred, oldcred);
        if (ngrp < 1) {
                /*
                 * setgroups(0, NULL) is a legitimate way of clearing the
                 * groups vector on non-BSD systems (which generally do not
                 * have the egid in the groups[0]).  We risk security holes
                 * when running non-BSD software if we do not do the same.
                 */
                newcred->cr_ngroups = 1;
        } else {
                bcopy(groups, newcred->cr_groups, ngrp * sizeof(gid_t));
                newcred->cr_ngroups = ngrp;
        }
        setsugid(p);
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct setreuid_args {
        uid_t   ruid;
        uid_t   euid;
};
#endif
/* ARGSUSED */
int
setreuid(register struct thread *td, struct setreuid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        uid_t euid, ruid;
        struct uidinfo *euip, *ruip;
        int error;

        euid = uap->euid;
        ruid = uap->ruid;
        AUDIT_ARG(euid, euid);
        AUDIT_ARG(ruid, ruid);
        newcred = crget();
        euip = uifind(euid);
        ruip = uifind(ruid);
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setreuid(p, oldcred, ruid, euid);
        if (error)
                goto fail;
#endif

        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 = priv_check_cred(oldcred, PRIV_CRED_SETREUID, 0)) != 0)
                goto fail;

        crcopy(newcred, oldcred);
        if (euid != (uid_t)-1 && oldcred->cr_uid != euid) {
                change_euid(newcred, euip);
                setsugid(p);
        }
        if (ruid != (uid_t)-1 && oldcred->cr_ruid != ruid) {
                change_ruid(newcred, ruip);
                setsugid(p);
        }
        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;
        PROC_UNLOCK(p);
        uifree(ruip);
        uifree(euip);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        uifree(ruip);
        uifree(euip);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct setregid_args {
        gid_t   rgid;
        gid_t   egid;
};
#endif
/* ARGSUSED */
int
setregid(register struct thread *td, struct setregid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        gid_t egid, rgid;
        int error;

        egid = uap->egid;
        rgid = uap->rgid;
        AUDIT_ARG(egid, egid);
        AUDIT_ARG(rgid, rgid);
        newcred = crget();
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setregid(p, oldcred, rgid, egid);
        if (error)
                goto fail;
#endif

        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 = priv_check_cred(oldcred, PRIV_CRED_SETREGID, 0)) != 0)
                goto fail;

        crcopy(newcred, oldcred);
        if (egid != (gid_t)-1 && oldcred->cr_groups[0] != egid) {
                change_egid(newcred, egid);
                setsugid(p);
        }
        if (rgid != (gid_t)-1 && oldcred->cr_rgid != rgid) {
                change_rgid(newcred, rgid);
                setsugid(p);
        }
        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);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        crfree(newcred);
        return (error);
}

/*
 * setresuid(ruid, euid, suid) is like setreuid except control over the saved
 * uid is explicit.
 */
#ifndef _SYS_SYSPROTO_H_
struct setresuid_args {
        uid_t   ruid;
        uid_t   euid;
        uid_t   suid;
};
#endif
/* ARGSUSED */
int
setresuid(register struct thread *td, struct setresuid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        uid_t euid, ruid, suid;
        struct uidinfo *euip, *ruip;
        int error;

        euid = uap->euid;
        ruid = uap->ruid;
        suid = uap->suid;
        AUDIT_ARG(euid, euid);
        AUDIT_ARG(ruid, ruid);
        AUDIT_ARG(suid, suid);
        newcred = crget();
        euip = uifind(euid);
        ruip = uifind(ruid);
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setresuid(p, oldcred, ruid, euid, suid);
        if (error)
                goto fail;
#endif

        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 = priv_check_cred(oldcred, PRIV_CRED_SETRESUID, 0)) != 0)
                goto fail;

        crcopy(newcred, oldcred);
        if (euid != (uid_t)-1 && oldcred->cr_uid != euid) {
                change_euid(newcred, euip);
                setsugid(p);
        }
        if (ruid != (uid_t)-1 && oldcred->cr_ruid != ruid) {
                change_ruid(newcred, ruip);
                setsugid(p);
        }
        if (suid != (uid_t)-1 && oldcred->cr_svuid != suid) {
                change_svuid(newcred, suid);
                setsugid(p);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        uifree(ruip);
        uifree(euip);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        uifree(ruip);
        uifree(euip);
        crfree(newcred);
        return (error);

}

/*
 * setresgid(rgid, egid, sgid) is like setregid except control over the saved
 * gid is explicit.
 */
#ifndef _SYS_SYSPROTO_H_
struct setresgid_args {
        gid_t   rgid;
        gid_t   egid;
        gid_t   sgid;
};
#endif
/* ARGSUSED */
int
setresgid(register struct thread *td, struct setresgid_args *uap)
{
        struct proc *p = td->td_proc;
        struct ucred *newcred, *oldcred;
        gid_t egid, rgid, sgid;
        int error;

        egid = uap->egid;
        rgid = uap->rgid;
        sgid = uap->sgid;
        AUDIT_ARG(egid, egid);
        AUDIT_ARG(rgid, rgid);
        AUDIT_ARG(sgid, sgid);
        newcred = crget();
        PROC_LOCK(p);
        oldcred = p->p_ucred;

#ifdef MAC
        error = mac_proc_check_setresgid(p, oldcred, rgid, egid, sgid);
        if (error)
                goto fail;
#endif

        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 = priv_check_cred(oldcred, PRIV_CRED_SETRESGID, 0)) != 0)
                goto fail;

        crcopy(newcred, oldcred);
        if (egid != (gid_t)-1 && oldcred->cr_groups[0] != egid) {
                change_egid(newcred, egid);
                setsugid(p);
        }
        if (rgid != (gid_t)-1 && oldcred->cr_rgid != rgid) {
                change_rgid(newcred, rgid);
                setsugid(p);
        }
        if (sgid != (gid_t)-1 && oldcred->cr_svgid != sgid) {
                change_svgid(newcred, sgid);
                setsugid(p);
        }
        p->p_ucred = newcred;
        PROC_UNLOCK(p);
        crfree(oldcred);
        return (0);

fail:
        PROC_UNLOCK(p);
        crfree(newcred);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct getresuid_args {
        uid_t   *ruid;
        uid_t   *euid;
        uid_t   *suid;
};
#endif
/* ARGSUSED */
int
getresuid(register struct thread *td, struct getresuid_args *uap)
{
        struct ucred *cred;
        int error1 = 0, error2 = 0, error3 = 0;

        cred = td->td_ucred;
        if (uap->ruid)
                error1 = copyout(&cred->cr_ruid,
                    uap->ruid, sizeof(cred->cr_ruid));
        if (uap->euid)
                error2 = copyout(&cred->cr_uid,
                    uap->euid, sizeof(cred->cr_uid));
        if (uap->suid)
                error3 = copyout(&cred->cr_svuid,
                    uap->suid, sizeof(cred->cr_svuid));
        return (error1 ? error1 : error2 ? error2 : error3);
}

#ifndef _SYS_SYSPROTO_H_
struct getresgid_args {
        gid_t   *rgid;
        gid_t   *egid;
        gid_t   *sgid;
};
#endif
/* ARGSUSED */
int
getresgid(register struct thread *td, struct getresgid_args *uap)
{
        struct ucred *cred;
        int error1 = 0, error2 = 0, error3 = 0;

        cred = td->td_ucred;
        if (uap->rgid)
                error1 = copyout(&cred->cr_rgid,
                    uap->rgid, sizeof(cred->cr_rgid));
        if (uap->egid)
                error2 = copyout(&cred->cr_groups[0],
                    uap->egid, sizeof(cred->cr_groups[0]));
        if (uap->sgid)
                error3 = copyout(&cred->cr_svgid,
                    uap->sgid, sizeof(cred->cr_svgid));
        return (error1 ? error1 : error2 ? error2 : error3);
}

#ifndef _SYS_SYSPROTO_H_
struct issetugid_args {
        int dummy;
};
#endif
/* ARGSUSED */
int
issetugid(register struct thread *td, struct issetugid_args *uap)
{
        struct proc *p = td->td_proc;

        /*
         * Note: OpenBSD sets a P_SUGIDEXEC flag set at execve() time,
         * we use P_SUGID because we consider changing the owners as
         * "tainting" as well.
         * This is significant for procs that start as root and "become"
         * a user without an exec - programs cannot know *everything*
         * that libc *might* have put in their data segment.
         */
        PROC_LOCK(p);
        td->td_retval[0] = (p->p_flag & P_SUGID) ? 1 : 0;
        PROC_UNLOCK(p);
        return (0);
}

int
__setugid(struct thread *td, struct __setugid_args *uap)
{
#ifdef REGRESSION
        struct proc *p;

        p = td->td_proc;
        switch (uap->flag) {
        case 0:
                PROC_LOCK(p);
                p->p_flag &= ~P_SUGID;
                PROC_UNLOCK(p);
                return (0);
        case 1:
                PROC_LOCK(p);
                p->p_flag |= P_SUGID;
                PROC_UNLOCK(p);
                return (0);
        default:
                return (EINVAL);
        }
#else /* !REGRESSION */

        return (ENOSYS);
#endif /* REGRESSION */
}

/*
 * Check if gid is a member of the group set.
 */
int
groupmember(gid_t gid, struct ucred *cred)
{
        register gid_t *gp;
        gid_t *egp;

        egp = &(cred->cr_groups[cred->cr_ngroups]);
        for (gp = cred->cr_groups; gp < egp; gp++)
                if (*gp == gid)
                        return (1);
        return (0);
}

/*
 * Test the active securelevel against a given level.  securelevel_gt()
 * implements (securelevel > level).  securelevel_ge() implements
 * (securelevel >= level).  Note that the logic is inverted -- these
 * functions return EPERM on "success" and 0 on "failure".
 *
 * XXXRW: Possibly since this has to do with privilege, it should move to
 * kern_priv.c.
 */
int
securelevel_gt(struct ucred *cr, int level)
{
        int active_securelevel;

        active_securelevel = securelevel;
        KASSERT(cr != NULL, ("securelevel_gt: null cr"));
        if (cr->cr_prison != NULL)
                active_securelevel = imax(cr->cr_prison->pr_securelevel,
                    active_securelevel);
        return (active_securelevel > level ? EPERM : 0);
}

int
securelevel_ge(struct ucred *cr, int level)
{
        int active_securelevel;

        active_securelevel = securelevel;
        KASSERT(cr != NULL, ("securelevel_ge: null cr"));
        if (cr->cr_prison != NULL)
                active_securelevel = imax(cr->cr_prison->pr_securelevel,
                    active_securelevel);
        return (active_securelevel >= level ? EPERM : 0);
}

/*
 * 'see_other_uids' determines whether or not visibility of processes
 * and sockets with credentials holding different real uids is possible
 * using a variety of system MIBs.
 * XXX: data declarations should be together near the beginning of the file.
 */
static int      see_other_uids = 1;
SYSCTL_INT(_security_bsd, OID_AUTO, see_other_uids, CTLFLAG_RW,
    &see_other_uids, 0,
    "Unprivileged processes may see subjects/objects with different real uid");

/*-
 * Determine if u1 "can see" the subject specified by u2, according to the
 * 'see_other_uids' policy.
 * Returns: 0 for permitted, ESRCH otherwise
 * Locks: none
 * References: *u1 and *u2 must not change during the call
 *             u1 may equal u2, in which case only one reference is required
 */
static int
cr_seeotheruids(struct ucred *u1, struct ucred *u2)
{

        if (!see_other_uids && u1->cr_ruid != u2->cr_ruid) {
                if (priv_check_cred(u1, PRIV_SEEOTHERUIDS, 0) != 0)
                        return (ESRCH);
        }
        return (0);
}

/*
 * 'see_other_gids' determines whether or not visibility of processes
 * and sockets with credentials holding different real gids is possible
 * using a variety of system MIBs.
 * XXX: data declarations should be together near the beginning of the file.
 */
static int      see_other_gids = 1;
SYSCTL_INT(_security_bsd, OID_AUTO, see_other_gids, CTLFLAG_RW,
    &see_other_gids, 0,
    "Unprivileged processes may see subjects/objects with different real gid");

/*
 * Determine if u1 can "see" the subject specified by u2, according to the
 * 'see_other_gids' policy.
 * Returns: 0 for permitted, ESRCH otherwise
 * Locks: none
 * References: *u1 and *u2 must not change during the call
 *             u1 may equal u2, in which case only one reference is required
 */
static int
cr_seeothergids(struct ucred *u1, struct ucred *u2)
{
        int i, match;
        
        if (!see_other_gids) {
                match = 0;
                for (i = 0; i < u1->cr_ngroups; i++) {
                        if (groupmember(u1->cr_groups[i], u2))
                                match = 1;
                        if (match)
                                break;
                }
                if (!match) {
                        if (priv_check_cred(u1, PRIV_SEEOTHERGIDS, 0) != 0)
                                return (ESRCH);
                }
        }
        return (0);
}

/*-
 * Determine if u1 "can see" the subject specified by u2.
 * Returns: 0 for permitted, an errno value otherwise
 * Locks: none
 * References: *u1 and *u2 must not change during the call
 *             u1 may equal u2, in which case only one reference is required
 */
int
cr_cansee(struct ucred *u1, struct ucred *u2)
{
        int error;

        if ((error = prison_check(u1, u2)))
                return (error);
#ifdef MAC
        if ((error = mac_cred_check_visible(u1, u2)))
                return (error);
#endif
        if ((error = cr_seeotheruids(u1, u2)))
                return (error);
        if ((error = cr_seeothergids(u1, u2)))
                return (error);
        return (0);
}

/*-
 * Determine if td "can see" the subject specified by p.
 * Returns: 0 for permitted, an errno value otherwise
 * Locks: Sufficient locks to protect p->p_ucred must be held.  td really
 *        should be curthread.
 * References: td and p must be valid for the lifetime of the call
 */
int
p_cansee(struct thread *td, struct proc *p)
{

        /* Wrap cr_cansee() for all functionality. */
        KASSERT(td == curthread, ("%s: td not curthread", __func__));
        PROC_LOCK_ASSERT(p, MA_OWNED);
        return (cr_cansee(td->td_ucred, p->p_ucred));
}

/*
 * 'conservative_signals' prevents the delivery of a broad class of
 * signals by unprivileged processes to processes that have changed their
 * credentials since the last invocation of execve().  This can prevent
 * the leakage of cached information or retained privileges as a result
 * of a common class of signal-related vulnerabilities.  However, this
 * may interfere with some applications that expect to be able to
 * deliver these signals to peer processes after having given up
 * privilege.
 */
static int      conservative_signals = 1;
SYSCTL_INT(_security_bsd, OID_AUTO, conservative_signals, CTLFLAG_RW,
    &conservative_signals, 0, "Unprivileged processes prevented from "
    "sending certain signals to processes whose credentials have changed");
/*-
 * Determine whether cred may deliver the specified signal to proc.
 * Returns: 0 for permitted, an errno value otherwise.
 * Locks: A lock must be held for proc.
 * References: cred and proc must be valid for the lifetime of the call.
 */
int
cr_cansignal(struct ucred *cred, struct proc *proc, int signum)
{
        int error;

        PROC_LOCK_ASSERT(proc, MA_OWNED);
        /*
         * Jail semantics limit the scope of signalling to proc in the
         * same jail as cred, if cred is in jail.
         */
        error = prison_check(cred, proc->p_ucred);
        if (error)
                return (error);
#ifdef MAC
        if ((error = mac_proc_check_signal(cred, proc, signum)))
                return (error);
#endif
        if ((error = cr_seeotheruids(cred, proc->p_ucred)))
                return (error);
        if ((error = cr_seeothergids(cred, proc->p_ucred)))
                return (error);

        /*
         * UNIX signal semantics depend on the status of the P_SUGID
         * bit on the target process.  If the bit is set, then additional
         * restrictions are placed on the set of available signals.
         */
        if (conservative_signals && (proc->p_flag & P_SUGID)) {
                switch (signum) {
                case 0:
                case SIGKILL:
                case SIGINT:
                case SIGTERM:
                case SIGALRM:
                case SIGSTOP:
                case SIGTTIN:
                case SIGTTOU:
                case SIGTSTP:
                case SIGHUP:
                case SIGUSR1:
                case SIGUSR2:
                        /*
                         * Generally, permit job and terminal control
                         * signals.
                         */
                        break;
                default:
                        /* Not permitted without privilege. */
                        error = priv_check_cred(cred, PRIV_SIGNAL_SUGID, 0);
                        if (error)
                                return (error);
                }
        }

        /*
         * Generally, the target credential's ruid or svuid must match the
         * subject credential's ruid or euid.
         */
        if (cred->cr_ruid != proc->p_ucred->cr_ruid &&
            cred->cr_ruid != proc->p_ucred->cr_svuid &&
            cred->cr_uid != proc->p_ucred->cr_ruid &&
            cred->cr_uid != proc->p_ucred->cr_svuid) {
                error = priv_check_cred(cred, PRIV_SIGNAL_DIFFCRED, 0);
                if (error)
                        return (error);
        }

        return (0);
}

/*-
 * Determine whether td may deliver the specified signal to p.
 * Returns: 0 for permitted, an errno value otherwise
 * Locks: Sufficient locks to protect various components of td and p
 *        must be held.  td must be curthread, and a lock must be
 *        held for p.
 * References: td and p must be valid for the lifetime of the call
 */
int
p_cansignal(struct thread *td, struct proc *p, int signum)
{

        KASSERT(td == curthread, ("%s: td not curthread", __func__));
        PROC_LOCK_ASSERT(p, MA_OWNED);
        if (td->td_proc == p)
                return (0);

        /*
         * UNIX signalling semantics require that processes in the same
         * session always be able to deliver SIGCONT to one another,
         * overriding the remaining protections.
         */
        /* XXX: This will require an additional lock of some sort. */
        if (signum == SIGCONT && td->td_proc->p_session == p->p_session)
                return (0);
        /*
         * Some compat layers use SIGTHR and higher signals for
         * communication between different kernel threads of the same
         * process, so that they expect that it's always possible to
         * deliver them, even for suid applications where cr_cansignal() can
         * deny such ability for security consideration.  It should be
         * pretty safe to do since the only way to create two processes
         * with the same p_leader is via rfork(2).
         */
        if (td->td_proc->p_leader != NULL && signum >= SIGTHR &&
            signum < SIGTHR + 4 && td->td_proc->p_leader == p->p_leader)
                return (0);

        return (cr_cansignal(td->td_ucred, p, signum));
}

/*-
 * Determine whether td may reschedule p.
 * Returns: 0 for permitted, an errno value otherwise
 * Locks: Sufficient locks to protect various components of td and p
 *        must be held.  td must be curthread, and a lock must
 *        be held for p.
 * References: td and p must be valid for the lifetime of the call
 */
int
p_cansched(struct thread *td, struct proc *p)
{
        int error;

        KASSERT(td == curthread, ("%s: td not curthread", __func__));
        PROC_LOCK_ASSERT(p, MA_OWNED);
        if (td->td_proc == p)
                return (0);
        if ((error = prison_check(td->td_ucred, p->p_ucred)))
                return (error);
#ifdef MAC
        if ((error = mac_proc_check_sched(td->td_ucred, p)))
                return (error);
#endif
        if ((error = cr_seeotheruids(td->td_ucred, p->p_ucred)))
                return (error);
        if ((error = cr_seeothergids(td->td_ucred, p->p_ucred)))
                return (error);
        if (td->td_ucred->cr_ruid != p->p_ucred->cr_ruid &&
            td->td_ucred->cr_uid != p->p_ucred->cr_ruid) {
                error = priv_check(td, PRIV_SCHED_DIFFCRED);
                if (error)
                        return (error);
        }
        return (0);
}

/*
 * The 'unprivileged_proc_debug' flag may be used to disable a variety of
 * unprivileged inter-process debugging services, including some procfs
 * functionality, ptrace(), and ktrace().  In the past, inter-process
 * debugging has been involved in a variety of security problems, and sites
 * not requiring the service might choose to disable it when hardening
 * systems.
 *
 * XXX: Should modifying and reading this variable require locking?
 * XXX: data declarations should be together near the beginning of the file.
 */
static int      unprivileged_proc_debug = 1;
SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_proc_debug, CTLFLAG_RW,
    &unprivileged_proc_debug, 0,
    "Unprivileged processes may use process debugging facilities");

/*-
 * Determine whether td may debug p.
 * Returns: 0 for permitted, an errno value otherwise
 * Locks: Sufficient locks to protect various components of td and p
 *        must be held.  td must be curthread, and a lock must
 *        be held for p.
 * References: td and p must be valid for the lifetime of the call
 */
int
p_candebug(struct thread *td, struct proc *p)
{
        int credentialchanged, error, grpsubset, i, uidsubset;

        KASSERT(td == curthread, ("%s: td not curthread", __func__));
        PROC_LOCK_ASSERT(p, MA_OWNED);
        if (!unprivileged_proc_debug) {
                error = priv_check(td, PRIV_DEBUG_UNPRIV);
                if (error)
                        return (error);
        }
        if (td->td_proc == p)
                return (0);
        if ((error = prison_check(td->td_ucred, p->p_ucred)))
                return (error);
#ifdef MAC
        if ((error = mac_proc_check_debug(td->td_ucred, p)))
                return (error);
#endif
        if ((error = cr_seeotheruids(td->td_ucred, p->p_ucred)))
                return (error);
        if ((error = cr_seeothergids(td->td_ucred, p->p_ucred)))
                return (error);

        /*
         * Is p's group set a subset of td's effective group set?  This
         * includes p's egid, group access list, rgid, and svgid.
         */
        grpsubset = 1;
        for (i = 0; i < p->p_ucred->cr_ngroups; i++) {
                if (!groupmember(p->p_ucred->cr_groups[i], td->td_ucred)) {
                        grpsubset = 0;
                        break;
                }
        }
        grpsubset = grpsubset &&
            groupmember(p->p_ucred->cr_rgid, td->td_ucred) &&
            groupmember(p->p_ucred->cr_svgid, td->td_ucred);

        /*
         * Are the uids present in p's credential equal to td's
         * effective uid?  This includes p's euid, svuid, and ruid.
         */
        uidsubset = (td->td_ucred->cr_uid == p->p_ucred->cr_uid &&
            td->td_ucred->cr_uid == p->p_ucred->cr_svuid &&
            td->td_ucred->cr_uid == p->p_ucred->cr_ruid);

        /*
         * Has the credential of the process changed since the last exec()?
         */
        credentialchanged = (p->p_flag & P_SUGID);

        /*
         * If p's gids aren't a subset, or the uids aren't a subset,
         * or the credential has changed, require appropriate privilege
         * for td to debug p.
         */
        if (!grpsubset || !uidsubset) {
                error = priv_check(td, PRIV_DEBUG_DIFFCRED);
                if (error)
                        return (error);
        }

        if (credentialchanged) {
                error = priv_check(td, PRIV_DEBUG_SUGID);
                if (error)
                        return (error);
        }

        /* Can't trace init when securelevel > 0. */
        if (p == initproc) {
                error = securelevel_gt(td->td_ucred, 0);
                if (error)
                        return (error);
        }

        /*
         * Can't trace a process that's currently exec'ing.
         *
         * XXX: Note, this is not a security policy decision, it's a
         * basic correctness/functionality decision.  Therefore, this check
         * should be moved to the caller's of p_candebug().
         */
        if ((p->p_flag & P_INEXEC) != 0)
                return (EAGAIN);

        return (0);
}

/*-
 * Determine whether the subject represented by cred can "see" a socket.
 * Returns: 0 for permitted, ENOENT otherwise.
 */
int
cr_canseesocket(struct ucred *cred, struct socket *so)
{
        int error;

        error = prison_check(cred, so->so_cred);
        if (error)
                return (ENOENT);
#ifdef MAC
        SOCK_LOCK(so);
        error = mac_socket_check_visible(cred, so);
        SOCK_UNLOCK(so);
        if (error)
                return (error);
#endif
        if (cr_seeotheruids(cred, so->so_cred))
                return (ENOENT);
        if (cr_seeothergids(cred, so->so_cred))
                return (ENOENT);

        return (0);
}

/*-
 * Determine whether td can wait for the exit of p.
 * Returns: 0 for permitted, an errno value otherwise
 * Locks: Sufficient locks to protect various components of td and p
 *        must be held.  td must be curthread, and a lock must
 *        be held for p.
 * References: td and p must be valid for the lifetime of the call

 */
int
p_canwait(struct thread *td, struct proc *p)
{
        int error;

        KASSERT(td == curthread, ("%s: td not curthread", __func__));
        PROC_LOCK_ASSERT(p, MA_OWNED);
        if ((error = prison_check(td->td_ucred, p->p_ucred)))
                return (error);
#ifdef MAC
        if ((error = mac_proc_check_wait(td->td_ucred, p)))
                return (error);
#endif
#if 0
        /* XXXMAC: This could have odd effects on some shells. */
        if ((error = cr_seeotheruids(td->td_ucred, p->p_ucred)))
                return (error);
#endif

        return (0);
}

/*
 * Allocate a zeroed cred structure.
 */
struct ucred *
crget(void)
{
        register struct ucred *cr;

        MALLOC(cr, struct ucred *, sizeof(*cr), M_CRED, M_WAITOK | M_ZERO);
        refcount_init(&cr->cr_ref, 1);
#ifdef AUDIT
        audit_cred_init(cr);
#endif
#ifdef MAC
        mac_cred_init(cr);
#endif
        return (cr);
}

/*
 * Claim another reference to a ucred structure.
 */
struct ucred *
crhold(struct ucred *cr)
{

        refcount_acquire(&cr->cr_ref);
        return (cr);
}

/*
 * Free a cred structure.  Throws away space when ref count gets to 0.
 */
void
crfree(struct ucred *cr)
{

        KASSERT(cr->cr_ref > 0, ("bad ucred refcount: %d", cr->cr_ref));
        KASSERT(cr->cr_ref != 0xdeadc0de, ("dangling reference to ucred"));
        if (refcount_release(&cr->cr_ref)) {
                /*
                 * Some callers of crget(), such as nfs_statfs(),
                 * allocate a temporary credential, but don't
                 * allocate a uidinfo structure.
                 */
                if (cr->cr_uidinfo != NULL)
                        uifree(cr->cr_uidinfo);
                if (cr->cr_ruidinfo != NULL)
                        uifree(cr->cr_ruidinfo);
                /*
                 * Free a prison, if any.
                 */
                if (jailed(cr))
                        prison_free(cr->cr_prison);
#ifdef AUDIT
                audit_cred_destroy(cr);
#endif
#ifdef MAC
                mac_cred_destroy(cr);
#endif
                FREE(cr, M_CRED);
        }
}

/*
 * Check to see if this ucred is shared.
 */
int
crshared(struct ucred *cr)
{

        return (cr->cr_ref > 1);
}

/*
 * Copy a ucred's contents from a template.  Does not block.
 */
void
crcopy(struct ucred *dest, struct ucred *src)
{

        KASSERT(crshared(dest) == 0, ("crcopy of shared ucred"));
        bcopy(&src->cr_startcopy, &dest->cr_startcopy,
            (unsigned)((caddr_t)&src->cr_endcopy -
                (caddr_t)&src->cr_startcopy));
        uihold(dest->cr_uidinfo);
        uihold(dest->cr_ruidinfo);
        if (jailed(dest))
                prison_hold(dest->cr_prison);
#ifdef AUDIT
        audit_cred_copy(src, dest);
#endif
#ifdef MAC
        mac_cred_copy(src, dest);
#endif
}

/*
 * Dup cred struct to a new held one.
 */
struct ucred *
crdup(struct ucred *cr)
{
        struct ucred *newcr;

        newcr = crget();
        crcopy(newcr, cr);
        return (newcr);
}

/*
 * Fill in a struct xucred based on a struct ucred.
 */
void
cru2x(struct ucred *cr, struct xucred *xcr)
{

        bzero(xcr, sizeof(*xcr));
        xcr->cr_version = XUCRED_VERSION;
        xcr->cr_uid = cr->cr_uid;
        xcr->cr_ngroups = cr->cr_ngroups;
        bcopy(cr->cr_groups, xcr->cr_groups, sizeof(cr->cr_groups));
}

/*
 * small routine to swap a thread's current ucred for the correct one taken
 * from the process.
 */
void
cred_update_thread(struct thread *td)
{
        struct proc *p;
        struct ucred *cred;

        p = td->td_proc;
        cred = td->td_ucred;
        PROC_LOCK(p);
        td->td_ucred = crhold(p->p_ucred);
        PROC_UNLOCK(p);
        if (cred != NULL)
                crfree(cred);
}

/*
 * Get login name, if available.
 */
#ifndef _SYS_SYSPROTO_H_
struct getlogin_args {
        char    *namebuf;
        u_int   namelen;
};
#endif
/* ARGSUSED */
int
getlogin(struct thread *td, struct getlogin_args *uap)
{
        int error;
        char login[MAXLOGNAME];
        struct proc *p = td->td_proc;

        if (uap->namelen > MAXLOGNAME)
                uap->namelen = MAXLOGNAME;
        PROC_LOCK(p);
        SESS_LOCK(p->p_session);
        bcopy(p->p_session->s_login, login, uap->namelen);
        SESS_UNLOCK(p->p_session);
        PROC_UNLOCK(p);
        error = copyout(login, uap->namebuf, uap->namelen);
        return(error);
}

/*
 * Set login name.
 */
#ifndef _SYS_SYSPROTO_H_
struct setlogin_args {
        char    *namebuf;
};
#endif
/* ARGSUSED */
int
setlogin(struct thread *td, struct setlogin_args *uap)
{
        struct proc *p = td->td_proc;
        int error;
        char logintmp[MAXLOGNAME];

        error = priv_check(td, PRIV_PROC_SETLOGIN);
        if (error)
                return (error);
        error = copyinstr(uap->namebuf, logintmp, sizeof(logintmp), NULL);
        if (error == ENAMETOOLONG)
                error = EINVAL;
        else if (!error) {
                PROC_LOCK(p);
                SESS_LOCK(p->p_session);
                (void) memcpy(p->p_session->s_login, logintmp,
                    sizeof(logintmp));
                SESS_UNLOCK(p->p_session);
                PROC_UNLOCK(p);
        }
        return (error);
}

void
setsugid(struct proc *p)
{

        PROC_LOCK_ASSERT(p, MA_OWNED);
        p->p_flag |= P_SUGID;
        if (!(p->p_pfsflags & PF_ISUGID))
                p->p_stops = 0;
}

/*-
 * 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(struct ucred *newcred, struct uidinfo *euip)
{

        newcred->cr_uid = euip->ui_uid;
        uihold(euip);
        uifree(newcred->cr_uidinfo);
        newcred->cr_uidinfo = euip;
}

/*-
 * 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_egid(struct ucred *newcred, gid_t egid)
{

        newcred->cr_groups[0] = egid;
}

/*-
 * 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(struct ucred *newcred, struct uidinfo *ruip)
{

        (void)chgproccnt(newcred->cr_ruidinfo, -1, 0);
        newcred->cr_ruid = ruip->ui_uid;
        uihold(ruip);
        uifree(newcred->cr_ruidinfo);
        newcred->cr_ruidinfo = ruip;
        (void)chgproccnt(newcred->cr_ruidinfo, 1, 0);
}

/*-
 * 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(struct ucred *newcred, gid_t rgid)
{

        newcred->cr_rgid = rgid;
}

/*-
 * 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(struct ucred *newcred, uid_t svuid)
{

        newcred->cr_svuid = svuid;
}

/*-
 * 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(struct ucred *newcred, gid_t svgid)
{

        newcred->cr_svgid = svgid;
}