freebsd-src/sys/kern/sysv_ipc.c

/*	$NetBSD: sysv_ipc.c,v 1.7 1994/06/29 06:33:11 cgd Exp $	*/
/*-
 * Copyright (c) 1994 Herb Peyerl <hpeyerl@novatel.ca>
 * All rights reserved.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Herb Peyerl.
 * 4. The name of Herb Peyerl may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

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

#include "opt_sysvipc.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/proc.h>
#include <sys/ucred.h>

void (*shmfork_hook)(struct proc *, struct proc *) = NULL;
void (*shmexit_hook)(struct vmspace *) = NULL;

/* called from kern_fork.c */
void
shmfork(p1, p2)
	struct proc *p1, *p2;
{

	if (shmfork_hook != NULL)
		shmfork_hook(p1, p2);
	return;
}

/* called from kern_exit.c */
void
shmexit(struct vmspace *vm)
{

	if (shmexit_hook != NULL)
		shmexit_hook(vm);
	return;
}

/*
 * Check for IPC permission.
 *
 * Note: The MAC Framework does not require any modifications to the
 * ipcperm() function, as access control checks are performed throughout the
 * implementation of each primitive.  Those entry point calls complement the
 * ipcperm() discertionary checks.
 */
int
ipcperm(td, perm, mode)
	struct thread *td;
	struct ipc_perm *perm;
	int mode;
{
	struct ucred *cred = td->td_ucred;
	int error;

	if (cred->cr_uid != perm->cuid && cred->cr_uid != perm->uid) {
		/*
		 * For a non-create/owner, we require privilege to
		 * modify the object protections.  Note: some other
		 * implementations permit IPC_M to be delegated to
		 * unprivileged non-creator/owner uids/gids.
		 */
		if (mode & IPC_M) {
			error = suser(td);
			if (error)
				return (error);
		}
		/*
		 * Try to match against creator/owner group; if not, fall
		 * back on other.
		 */
		mode >>= 3;
		if (!groupmember(perm->gid, cred) &&
		    !groupmember(perm->cgid, cred))
			mode >>= 3;
	} else {
		/*
		 * Always permit the creator/owner to update the object
		 * protections regardless of whether the object mode
		 * permits it.
		 */
		if (mode & IPC_M)
			return (0);
	}

	if ((mode & perm->mode) != mode) {
		if (suser(td) != 0)
			return (EACCES);
	}
	return (0);
}