示例#1
0
int
sys_setegid(struct setegid_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	gid_t egid;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;
	egid = uap->egid;
	if (egid != cr->cr_rgid &&		/* allow setegid(getgid()) */
	    egid != cr->cr_svgid &&		/* allow setegid(saved gid) */
	    (error = priv_check_cred(cr, PRIV_CRED_SETEGID, 0))) {
		goto done;
	}
	if (cr->cr_groups[0] != egid) {
		cr = cratom(&p->p_ucred);
		cr->cr_groups[0] = egid;
		setsugid();
	}
	error = 0;
done:
	lwkt_reltoken(&proc_token);
	return (error);
}
示例#2
0
int
sys_seteuid(struct seteuid_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	uid_t euid;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;
	euid = uap->euid;
	if (euid != cr->cr_ruid &&		/* allow seteuid(getuid()) */
	    euid != cr->cr_svuid &&		/* allow seteuid(saved uid) */
	    (error = priv_check_cred(cr, PRIV_CRED_SETEUID, 0))) {
		lwkt_reltoken(&proc_token);
		return (error);
	}

	/*
	 * Everything's okay, do it.  Copy credentials so other references do
	 * not see our changes.
	 */
	if (cr->cr_uid != euid) {
		change_euid(euid);
		setsugid();
	}
	lwkt_reltoken(&proc_token);
	return (0);
}
示例#3
0
/*
 * setresgid(rgid, egid, sgid) is like setregid except control over the
 * saved gid is explicit.
 */
int
sys_setresgid(struct setresgid_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	gid_t rgid, egid, sgid;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;
	rgid = uap->rgid;
	egid = uap->egid;
	sgid = uap->sgid;
	if (((rgid != (gid_t)-1 && rgid != cr->cr_rgid && rgid != cr->cr_svgid &&
	      rgid != cr->cr_groups[0]) ||
	     (egid != (gid_t)-1 && egid != cr->cr_rgid && egid != cr->cr_svgid &&
	      egid != cr->cr_groups[0]) ||
	     (sgid != (gid_t)-1 && sgid != cr->cr_rgid && sgid != cr->cr_svgid &&
	      sgid != cr->cr_groups[0])) &&
	    (error = priv_check_cred(cr, PRIV_CRED_SETRESGID, 0)) != 0) {
		goto done;
	}

	if (egid != (gid_t)-1 && cr->cr_groups[0] != egid) {
		cr = cratom(&p->p_ucred);
		cr->cr_groups[0] = egid;
		setsugid();
	}
	if (rgid != (gid_t)-1 && cr->cr_rgid != rgid) {
		cr = cratom(&p->p_ucred);
		cr->cr_rgid = rgid;
		setsugid();
	}
	if (sgid != (gid_t)-1 && cr->cr_svgid != sgid) {
		cr = cratom(&p->p_ucred);
		cr->cr_svgid = sgid;
		setsugid();
	}
	error = 0;
done:
	lwkt_reltoken(&proc_token);
	return (error);
}
示例#4
0
/*
 * setresuid(ruid, euid, suid) is like setreuid except control over the
 * saved uid is explicit.
 */
int
sys_setresuid(struct setresuid_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	uid_t ruid, euid, suid;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;

	ruid = uap->ruid;
	euid = uap->euid;
	suid = uap->suid;
	if (((ruid != (uid_t)-1 && ruid != cr->cr_ruid && ruid != cr->cr_svuid &&
	      ruid != cr->cr_uid) ||
	     (euid != (uid_t)-1 && euid != cr->cr_ruid && euid != cr->cr_svuid &&
	      euid != cr->cr_uid) ||
	     (suid != (uid_t)-1 && suid != cr->cr_ruid && suid != cr->cr_svuid &&
	      suid != cr->cr_uid)) &&
	    (error = priv_check_cred(cr, PRIV_CRED_SETRESUID, 0)) != 0) {
		goto done;
	}
	if (euid != (uid_t)-1 && cr->cr_uid != euid) {
		cr = change_euid(euid);
		setsugid();
	}
	if (ruid != (uid_t)-1 && cr->cr_ruid != ruid) {
		cr = change_ruid(ruid);
		setsugid();
	}
	if (suid != (uid_t)-1 && cr->cr_svuid != suid) {
		cr = cratom(&p->p_ucred);
		cr->cr_svuid = suid;
		setsugid();
	}
	error = 0;
done:
	lwkt_reltoken(&proc_token);
	return (error);
}
示例#5
0
int
linux_setgroups16(struct proc *p, struct linux_setgroups16_args *args)
{
	struct ucred *newcred, *oldcred;
	l_gid16_t linux_gidset[NGROUPS];
	gid_t *bsd_gidset;
	int ngrp, error;

#ifdef DEBUG
	if (ldebug(setgroups16))
		printf(ARGS(setgroups16, "%d, *"), args->gidsetsize);
#endif

	ngrp = args->gidsetsize;
	oldcred = p->p_ucred;

	/*
	 * cr_groups[0] holds egid. Setting the whole set from
	 * the supplied set will cause egid to be changed too.
	 * Keep cr_groups[0] unchanged to prevent that.
	 */

	if ((error = suser_xxx(oldcred, NULL, PRISON_ROOT)) != 0)
		return (error);

	if (ngrp >= NGROUPS)
		return (EINVAL);

	newcred = crdup(oldcred);
	if (ngrp > 0) {
		error = copyin((caddr_t)args->gidset, linux_gidset,
		    ngrp * sizeof(l_gid16_t));
		if (error)
			return (error);

		newcred->cr_ngroups = ngrp + 1;

		bsd_gidset = newcred->cr_groups;
		ngrp--;
		while (ngrp >= 0) {
			bsd_gidset[ngrp + 1] = linux_gidset[ngrp];
			ngrp--;
		}
	}
	else
		newcred->cr_ngroups = 1;

	setsugid(p);
	p->p_ucred = newcred;
	crfree(oldcred);
	return (0);
}
示例#6
0
int
sys_setgroups(struct setgroups_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	u_int ngrp;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;

	if ((error = priv_check_cred(cr, PRIV_CRED_SETGROUPS, 0)))
		goto done;
	ngrp = uap->gidsetsize;
	if (ngrp > NGROUPS) {
		error = EINVAL;
		goto done;
	}
	/*
	 * XXX A little bit lazy here.  We could test if anything has
	 * changed before cratom() and setting P_SUGID.
	 */
	cr = cratom(&p->p_ucred);
	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.
		 */
		cr->cr_ngroups = 1;
	} else {
		error = copyin(uap->gidset, cr->cr_groups,
			       ngrp * sizeof(gid_t));
		if (error)
			goto done;
		cr->cr_ngroups = ngrp;
	}
	setsugid();
	error = 0;
done:
	lwkt_reltoken(&proc_token);
	return (error);
}
示例#7
0
int
sys_setgid(struct setgid_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	gid_t gid;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;

	/*
	 * 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.
	 */
	gid = uap->gid;
	if (gid != cr->cr_rgid &&		/* allow setgid(getgid()) */
#ifdef _POSIX_SAVED_IDS
	    gid != cr->cr_svgid &&		/* allow setgid(saved gid) */
#endif
#ifdef POSIX_APPENDIX_B_4_2_2	/* Use BSD-compat clause from B.4.2.2 */
	    gid != cr->cr_groups[0] && /* allow setgid(getegid()) */
#endif
	    (error = priv_check_cred(cr, PRIV_CRED_SETGID, 0))) {
		goto done;
	}

#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 == cr->cr_groups[0] ||
#endif
	    priv_check_cred(cr, PRIV_CRED_SETGID, 0) == 0) /* we are using privs */
#endif
	{
		/*
		 * Set real gid
		 */
		if (cr->cr_rgid != gid) {
			cr = cratom(&p->p_ucred);
			cr->cr_rgid = gid;
			setsugid();
		}
		/*
		 * 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 (cr->cr_svgid != gid) {
			cr = cratom(&p->p_ucred);
			cr->cr_svgid = gid;
			setsugid();
		}
	}
	/*
	 * In all cases permitted cases, we are changing the egid.
	 * Copy credentials so other references do not see our changes.
	 */
	if (cr->cr_groups[0] != gid) {
		cr = cratom(&p->p_ucred);
		cr->cr_groups[0] = gid;
		setsugid();
	}
	error = 0;
done:
	lwkt_reltoken(&proc_token);
	return (error);
}
示例#8
0
int
sys_setuid(struct setuid_args *uap)
{
	struct proc *p = curproc;
	struct ucred *cr;
	uid_t uid;
	int error;

	lwkt_gettoken(&proc_token);
	cr = p->p_ucred;

	/*
	 * 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 uid's are going to
	 *    change.  Determined by compile options.
	 * 3: Change euid last. (after tests in #2 for "appropriate privs")
	 */
	uid = uap->uid;
	if (uid != cr->cr_ruid &&		/* allow setuid(getuid()) */
#ifdef _POSIX_SAVED_IDS
	    uid != crc->cr_svuid &&		/* allow setuid(saved gid) */
#endif
#ifdef POSIX_APPENDIX_B_4_2_2	/* Use BSD-compat clause from B.4.2.2 */
	    uid != cr->cr_uid &&	/* allow setuid(geteuid()) */
#endif
	    (error = priv_check_cred(cr, PRIV_CRED_SETUID, 0)))
		goto done;

#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 == cr->cr_uid ||
#endif
	    priv_check_cred(cr, PRIV_CRED_SETUID, 0) == 0) /* we are using privs */
#endif
	{
		/*
		 * Set the real uid and transfer proc count to new user.
		 */
		if (uid != cr->cr_ruid) {
			cr = change_ruid(uid);
			setsugid();
		}
		/*
		 * 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 (cr->cr_svuid != uid) {
			cr = cratom(&p->p_ucred);
			cr->cr_svuid = uid;
			setsugid();
		}
	}

	/*
	 * In all permitted cases, we are changing the euid.
	 * Copy credentials so other references do not see our changes.
	 */
	if (cr->cr_uid != uid) {
		change_euid(uid);
		setsugid();
	}
	error = 0;
done:
	lwkt_reltoken(&proc_token);
	return (error);
}
示例#9
0
/*
 * In-kernel implementation of execve().  All arguments are assumed to be
 * userspace pointers from the passed thread.
 */
static int
do_execve(struct thread *td, struct image_args *args, struct mac *mac_p)
{
	struct proc *p = td->td_proc;
	struct nameidata nd;
	struct ucred *oldcred;
	struct uidinfo *euip = NULL;
	register_t *stack_base;
	int error, i;
	struct image_params image_params, *imgp;
	struct vattr attr;
	int (*img_first)(struct image_params *);
	struct pargs *oldargs = NULL, *newargs = NULL;
	struct sigacts *oldsigacts = NULL, *newsigacts = NULL;
#ifdef KTRACE
	struct vnode *tracevp = NULL;
	struct ucred *tracecred = NULL;
#endif
	struct vnode *oldtextvp = NULL, *newtextvp;
	int credential_changing;
	int textset;
#ifdef MAC
	struct label *interpvplabel = NULL;
	int will_transition;
#endif
#ifdef HWPMC_HOOKS
	struct pmckern_procexec pe;
#endif
	static const char fexecv_proc_title[] = "(fexecv)";

	imgp = &image_params;

	/*
	 * Lock the process and set the P_INEXEC flag to indicate that
	 * it should be left alone until we're done here.  This is
	 * necessary to avoid race conditions - e.g. in ptrace() -
	 * that might allow a local user to illicitly obtain elevated
	 * privileges.
	 */
	PROC_LOCK(p);
	KASSERT((p->p_flag & P_INEXEC) == 0,
	    ("%s(): process already has P_INEXEC flag", __func__));
	p->p_flag |= P_INEXEC;
	PROC_UNLOCK(p);

	/*
	 * Initialize part of the common data
	 */
	bzero(imgp, sizeof(*imgp));
	imgp->proc = p;
	imgp->attr = &attr;
	imgp->args = args;
	oldcred = p->p_ucred;

#ifdef MAC
	error = mac_execve_enter(imgp, mac_p);
	if (error)
		goto exec_fail;
#endif

	/*
	 * Translate the file name. namei() returns a vnode pointer
	 *	in ni_vp among other things.
	 *
	 * XXXAUDIT: It would be desirable to also audit the name of the
	 * interpreter if this is an interpreted binary.
	 */
	if (args->fname != NULL) {
		NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | FOLLOW | SAVENAME
		    | AUDITVNODE1, UIO_SYSSPACE, args->fname, td);
	}

	SDT_PROBE1(proc, , , exec, args->fname);

interpret:
	if (args->fname != NULL) {
#ifdef CAPABILITY_MODE
		/*
		 * While capability mode can't reach this point via direct
		 * path arguments to execve(), we also don't allow
		 * interpreters to be used in capability mode (for now).
		 * Catch indirect lookups and return a permissions error.
		 */
		if (IN_CAPABILITY_MODE(td)) {
			error = ECAPMODE;
			goto exec_fail;
		}
#endif
		error = namei(&nd);
		if (error)
			goto exec_fail;

		newtextvp = nd.ni_vp;
		imgp->vp = newtextvp;
	} else {
		AUDIT_ARG_FD(args->fd);
		/*
		 * Descriptors opened only with O_EXEC or O_RDONLY are allowed.
		 */
		error = fgetvp_exec(td, args->fd, &cap_fexecve_rights, &newtextvp);
		if (error)
			goto exec_fail;
		vn_lock(newtextvp, LK_EXCLUSIVE | LK_RETRY);
		AUDIT_ARG_VNODE1(newtextvp);
		imgp->vp = newtextvp;
	}

	/*
	 * Check file permissions (also 'opens' file)
	 */
	error = exec_check_permissions(imgp);
	if (error)
		goto exec_fail_dealloc;

	imgp->object = imgp->vp->v_object;
	if (imgp->object != NULL)
		vm_object_reference(imgp->object);

	/*
	 * Set VV_TEXT now so no one can write to the executable while we're
	 * activating it.
	 *
	 * Remember if this was set before and unset it in case this is not
	 * actually an executable image.
	 */
	textset = VOP_IS_TEXT(imgp->vp);
	VOP_SET_TEXT(imgp->vp);

	error = exec_map_first_page(imgp);
	if (error)
		goto exec_fail_dealloc;

	imgp->proc->p_osrel = 0;
	imgp->proc->p_fctl0 = 0;

	/*
	 * Implement image setuid/setgid.
	 *
	 * Determine new credentials before attempting image activators
	 * so that it can be used by process_exec handlers to determine
	 * credential/setid changes.
	 *
	 * Don't honor setuid/setgid if the filesystem prohibits it or if
	 * the process is being traced.
	 *
	 * We disable setuid/setgid/etc in capability mode on the basis
	 * that most setugid applications are not written with that
	 * environment in mind, and will therefore almost certainly operate
	 * incorrectly. In principle there's no reason that setugid
	 * applications might not be useful in capability mode, so we may want
	 * to reconsider this conservative design choice in the future.
	 *
	 * XXXMAC: For the time being, use NOSUID to also prohibit
	 * transitions on the file system.
	 */
	credential_changing = 0;
	credential_changing |= (attr.va_mode & S_ISUID) &&
	    oldcred->cr_uid != attr.va_uid;
	credential_changing |= (attr.va_mode & S_ISGID) &&
	    oldcred->cr_gid != attr.va_gid;
#ifdef MAC
	will_transition = mac_vnode_execve_will_transition(oldcred, imgp->vp,
	    interpvplabel, imgp);
	credential_changing |= will_transition;
#endif

	/* Don't inherit PROC_PDEATHSIG_CTL value if setuid/setgid. */
	if (credential_changing)
		imgp->proc->p_pdeathsig = 0;

	if (credential_changing &&
#ifdef CAPABILITY_MODE
	    ((oldcred->cr_flags & CRED_FLAG_CAPMODE) == 0) &&
#endif
	    (imgp->vp->v_mount->mnt_flag & MNT_NOSUID) == 0 &&
	    (p->p_flag & P_TRACED) == 0) {
		imgp->credential_setid = true;
		VOP_UNLOCK(imgp->vp, 0);
		imgp->newcred = crdup(oldcred);
		if (attr.va_mode & S_ISUID) {
			euip = uifind(attr.va_uid);
			change_euid(imgp->newcred, euip);
		}
		vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
		if (attr.va_mode & S_ISGID)
			change_egid(imgp->newcred, attr.va_gid);
		/*
		 * Implement correct POSIX saved-id behavior.
		 *
		 * XXXMAC: Note that the current logic will save the
		 * uid and gid if a MAC domain transition occurs, even
		 * though maybe it shouldn't.
		 */
		change_svuid(imgp->newcred, imgp->newcred->cr_uid);
		change_svgid(imgp->newcred, imgp->newcred->cr_gid);
	} else {
		/*
		 * Implement correct POSIX saved-id behavior.
		 *
		 * XXX: It's not clear that the existing behavior is
		 * POSIX-compliant.  A number of sources indicate that the
		 * saved uid/gid should only be updated if the new ruid is
		 * not equal to the old ruid, or the new euid is not equal
		 * to the old euid and the new euid is not equal to the old
		 * ruid.  The FreeBSD code always updates the saved uid/gid.
		 * Also, this code uses the new (replaced) euid and egid as
		 * the source, which may or may not be the right ones to use.
		 */
		if (oldcred->cr_svuid != oldcred->cr_uid ||
		    oldcred->cr_svgid != oldcred->cr_gid) {
			VOP_UNLOCK(imgp->vp, 0);
			imgp->newcred = crdup(oldcred);
			vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
			change_svuid(imgp->newcred, imgp->newcred->cr_uid);
			change_svgid(imgp->newcred, imgp->newcred->cr_gid);
		}
	}
	/* The new credentials are installed into the process later. */

	/*
	 * Do the best to calculate the full path to the image file.
	 */
	if (args->fname != NULL && args->fname[0] == '/')
		imgp->execpath = args->fname;
	else {
		VOP_UNLOCK(imgp->vp, 0);
		if (vn_fullpath(td, imgp->vp, &imgp->execpath,
		    &imgp->freepath) != 0)
			imgp->execpath = args->fname;
		vn_lock(imgp->vp, LK_EXCLUSIVE | LK_RETRY);
	}

	/*
	 *	If the current process has a special image activator it
	 *	wants to try first, call it.   For example, emulating shell
	 *	scripts differently.
	 */
	error = -1;
	if ((img_first = imgp->proc->p_sysent->sv_imgact_try) != NULL)
		error = img_first(imgp);

	/*
	 *	Loop through the list of image activators, calling each one.
	 *	An activator returns -1 if there is no match, 0 on success,
	 *	and an error otherwise.
	 */
	for (i = 0; error == -1 && execsw[i]; ++i) {
		if (execsw[i]->ex_imgact == NULL ||
		    execsw[i]->ex_imgact == img_first) {
			continue;
		}
		error = (*execsw[i]->ex_imgact)(imgp);
	}

	if (error) {
		if (error == -1) {
			if (textset == 0)
				VOP_UNSET_TEXT(imgp->vp);
			error = ENOEXEC;
		}
		goto exec_fail_dealloc;
	}

	/*
	 * Special interpreter operation, cleanup and loop up to try to
	 * activate the interpreter.
	 */
	if (imgp->interpreted) {
		exec_unmap_first_page(imgp);
		/*
		 * VV_TEXT needs to be unset for scripts.  There is a short
		 * period before we determine that something is a script where
		 * VV_TEXT will be set. The vnode lock is held over this
		 * entire period so nothing should illegitimately be blocked.
		 */
		VOP_UNSET_TEXT(imgp->vp);
		/* free name buffer and old vnode */
		if (args->fname != NULL)
			NDFREE(&nd, NDF_ONLY_PNBUF);
#ifdef MAC
		mac_execve_interpreter_enter(newtextvp, &interpvplabel);
#endif
		if (imgp->opened) {
			VOP_CLOSE(newtextvp, FREAD, td->td_ucred, td);
			imgp->opened = 0;
		}
		vput(newtextvp);
		vm_object_deallocate(imgp->object);
		imgp->object = NULL;
		imgp->credential_setid = false;
		if (imgp->newcred != NULL) {
			crfree(imgp->newcred);
			imgp->newcred = NULL;
		}
		imgp->execpath = NULL;
		free(imgp->freepath, M_TEMP);
		imgp->freepath = NULL;
		/* set new name to that of the interpreter */
		NDINIT(&nd, LOOKUP, LOCKLEAF | FOLLOW | SAVENAME,
		    UIO_SYSSPACE, imgp->interpreter_name, td);
		args->fname = imgp->interpreter_name;
		goto interpret;
	}

	/*
	 * NB: We unlock the vnode here because it is believed that none
	 * of the sv_copyout_strings/sv_fixup operations require the vnode.
	 */
	VOP_UNLOCK(imgp->vp, 0);

	if (disallow_high_osrel &&
	    P_OSREL_MAJOR(p->p_osrel) > P_OSREL_MAJOR(__FreeBSD_version)) {
		error = ENOEXEC;
		uprintf("Osrel %d for image %s too high\n", p->p_osrel,
		    imgp->execpath != NULL ? imgp->execpath : "<unresolved>");
		vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
		goto exec_fail_dealloc;
	}

	/* ABI enforces the use of Capsicum. Switch into capabilities mode. */
	if (SV_PROC_FLAG(p, SV_CAPSICUM))
		sys_cap_enter(td, NULL);

	/*
	 * Copy out strings (args and env) and initialize stack base.
	 */
	stack_base = (*p->p_sysent->sv_copyout_strings)(imgp);

	/*
	 * Stack setup.
	 */
	error = (*p->p_sysent->sv_fixup)(&stack_base, imgp);
	if (error != 0) {
		vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
		goto exec_fail_dealloc;
	}

	if (args->fdp != NULL) {
		/* Install a brand new file descriptor table. */
		fdinstall_remapped(td, args->fdp);
		args->fdp = NULL;
	} else {
		/*
		 * Keep on using the existing file descriptor table. For
		 * security and other reasons, the file descriptor table
		 * cannot be shared after an exec.
		 */
		fdunshare(td);
		/* close files on exec */
		fdcloseexec(td);
	}

	/*
	 * Malloc things before we need locks.
	 */
	i = exec_args_get_begin_envv(imgp->args) - imgp->args->begin_argv;
	/* Cache arguments if they fit inside our allowance */
	if (ps_arg_cache_limit >= i + sizeof(struct pargs)) {
		newargs = pargs_alloc(i);
		bcopy(imgp->args->begin_argv, newargs->ar_args, i);
	}

	/*
	 * For security and other reasons, signal handlers cannot
	 * be shared after an exec. The new process gets a copy of the old
	 * handlers. In execsigs(), the new process will have its signals
	 * reset.
	 */
	if (sigacts_shared(p->p_sigacts)) {
		oldsigacts = p->p_sigacts;
		newsigacts = sigacts_alloc();
		sigacts_copy(newsigacts, oldsigacts);
	}

	vn_lock(imgp->vp, LK_SHARED | LK_RETRY);

	PROC_LOCK(p);
	if (oldsigacts)
		p->p_sigacts = newsigacts;
	/* Stop profiling */
	stopprofclock(p);

	/* reset caught signals */
	execsigs(p);

	/* name this process - nameiexec(p, ndp) */
	bzero(p->p_comm, sizeof(p->p_comm));
	if (args->fname)
		bcopy(nd.ni_cnd.cn_nameptr, p->p_comm,
		    min(nd.ni_cnd.cn_namelen, MAXCOMLEN));
	else if (vn_commname(newtextvp, p->p_comm, sizeof(p->p_comm)) != 0)
		bcopy(fexecv_proc_title, p->p_comm, sizeof(fexecv_proc_title));
	bcopy(p->p_comm, td->td_name, sizeof(td->td_name));
#ifdef KTR
	sched_clear_tdname(td);
#endif

	/*
	 * mark as execed, wakeup the process that vforked (if any) and tell
	 * it that it now has its own resources back
	 */
	p->p_flag |= P_EXEC;
	if ((p->p_flag2 & P2_NOTRACE_EXEC) == 0)
		p->p_flag2 &= ~P2_NOTRACE;
	if (p->p_flag & P_PPWAIT) {
		p->p_flag &= ~(P_PPWAIT | P_PPTRACE);
		cv_broadcast(&p->p_pwait);
		/* STOPs are no longer ignored, arrange for AST */
		signotify(td);
	}

	/*
	 * Implement image setuid/setgid installation.
	 */
	if (imgp->credential_setid) {
		/*
		 * Turn off syscall tracing for set-id programs, except for
		 * root.  Record any set-id flags first to make sure that
		 * we do not regain any tracing during a possible block.
		 */
		setsugid(p);

#ifdef KTRACE
		if (p->p_tracecred != NULL &&
		    priv_check_cred(p->p_tracecred, PRIV_DEBUG_DIFFCRED))
			ktrprocexec(p, &tracecred, &tracevp);
#endif
		/*
		 * Close any file descriptors 0..2 that reference procfs,
		 * then make sure file descriptors 0..2 are in use.
		 *
		 * Both fdsetugidsafety() and fdcheckstd() may call functions
		 * taking sleepable locks, so temporarily drop our locks.
		 */
		PROC_UNLOCK(p);
		VOP_UNLOCK(imgp->vp, 0);
		fdsetugidsafety(td);
		error = fdcheckstd(td);
		vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
		if (error != 0)
			goto exec_fail_dealloc;
		PROC_LOCK(p);
#ifdef MAC
		if (will_transition) {
			mac_vnode_execve_transition(oldcred, imgp->newcred,
			    imgp->vp, interpvplabel, imgp);
		}
#endif
	} else {
		if (oldcred->cr_uid == oldcred->cr_ruid &&
		    oldcred->cr_gid == oldcred->cr_rgid)
			p->p_flag &= ~P_SUGID;
	}
	/*
	 * Set the new credentials.
	 */
	if (imgp->newcred != NULL) {
		proc_set_cred(p, imgp->newcred);
		crfree(oldcred);
		oldcred = NULL;
	}

	/*
	 * Store the vp for use in procfs.  This vnode was referenced by namei
	 * or fgetvp_exec.
	 */
	oldtextvp = p->p_textvp;
	p->p_textvp = newtextvp;

#ifdef KDTRACE_HOOKS
	/*
	 * Tell the DTrace fasttrap provider about the exec if it
	 * has declared an interest.
	 */
	if (dtrace_fasttrap_exec)
		dtrace_fasttrap_exec(p);
#endif

	/*
	 * Notify others that we exec'd, and clear the P_INEXEC flag
	 * as we're now a bona fide freshly-execed process.
	 */
	KNOTE_LOCKED(p->p_klist, NOTE_EXEC);
	p->p_flag &= ~P_INEXEC;

	/* clear "fork but no exec" flag, as we _are_ execing */
	p->p_acflag &= ~AFORK;

	/*
	 * Free any previous argument cache and replace it with
	 * the new argument cache, if any.
	 */
	oldargs = p->p_args;
	p->p_args = newargs;
	newargs = NULL;

	PROC_UNLOCK(p);

#ifdef	HWPMC_HOOKS
	/*
	 * Check if system-wide sampling is in effect or if the
	 * current process is using PMCs.  If so, do exec() time
	 * processing.  This processing needs to happen AFTER the
	 * P_INEXEC flag is cleared.
	 */
	if (PMC_SYSTEM_SAMPLING_ACTIVE() || PMC_PROC_IS_USING_PMCS(p)) {
		VOP_UNLOCK(imgp->vp, 0);
		pe.pm_credentialschanged = credential_changing;
		pe.pm_entryaddr = imgp->entry_addr;

		PMC_CALL_HOOK_X(td, PMC_FN_PROCESS_EXEC, (void *) &pe);
		vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
	}
#endif

	/* Set values passed into the program in registers. */
	(*p->p_sysent->sv_setregs)(td, imgp, (u_long)(uintptr_t)stack_base);

	vfs_mark_atime(imgp->vp, td->td_ucred);

	SDT_PROBE1(proc, , , exec__success, args->fname);

exec_fail_dealloc:
	if (imgp->firstpage != NULL)
		exec_unmap_first_page(imgp);

	if (imgp->vp != NULL) {
		if (args->fname)
			NDFREE(&nd, NDF_ONLY_PNBUF);
		if (imgp->opened)
			VOP_CLOSE(imgp->vp, FREAD, td->td_ucred, td);
		if (error != 0)
			vput(imgp->vp);
		else
			VOP_UNLOCK(imgp->vp, 0);
	}

	if (imgp->object != NULL)
		vm_object_deallocate(imgp->object);

	free(imgp->freepath, M_TEMP);

	if (error == 0) {
		if (p->p_ptevents & PTRACE_EXEC) {
			PROC_LOCK(p);
			if (p->p_ptevents & PTRACE_EXEC)
				td->td_dbgflags |= TDB_EXEC;
			PROC_UNLOCK(p);
		}

		/*
		 * Stop the process here if its stop event mask has
		 * the S_EXEC bit set.
		 */
		STOPEVENT(p, S_EXEC, 0);
	} else {
exec_fail:
		/* we're done here, clear P_INEXEC */
		PROC_LOCK(p);
		p->p_flag &= ~P_INEXEC;
		PROC_UNLOCK(p);

		SDT_PROBE1(proc, , , exec__failure, error);
	}

	if (imgp->newcred != NULL && oldcred != NULL)
		crfree(imgp->newcred);

#ifdef MAC
	mac_execve_exit(imgp);
	mac_execve_interpreter_exit(interpvplabel);
#endif
	exec_free_args(args);

	/*
	 * Handle deferred decrement of ref counts.
	 */
	if (oldtextvp != NULL)
		vrele(oldtextvp);
#ifdef KTRACE
	if (tracevp != NULL)
		vrele(tracevp);
	if (tracecred != NULL)
		crfree(tracecred);
#endif
	pargs_drop(oldargs);
	pargs_drop(newargs);
	if (oldsigacts != NULL)
		sigacts_free(oldsigacts);
	if (euip != NULL)
		uifree(euip);

	if (error && imgp->vmspace_destroyed) {
		/* sorry, no more process anymore. exit gracefully */
		exit1(td, 0, SIGABRT);
		/* NOT REACHED */
	}

#ifdef KTRACE
	if (error == 0)
		ktrprocctor(p);
#endif

	/*
	 * We don't want cpu_set_syscall_retval() to overwrite any of
	 * the register values put in place by exec_setregs().
	 * Implementations of cpu_set_syscall_retval() will leave
	 * registers unmodified when returning EJUSTRETURN.
	 */
	return (error == 0 ? EJUSTRETURN : error);
}