common/syscall/chdir.c

	chdir.c revision d3e55dcdc881b833a707e39ae1e12d8d5d35ad2d
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

/*
 * Portions of this source code were derived from Berkeley 4.3 BSD
 * under license from the Regents of the University of California.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/param.h>
#include <sys/isa_defs.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/cred.h>
#include <sys/user.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
#include <sys/pathname.h>
#include <sys/var.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/file.h>
#include <sys/mode.h>
#include <sys/proc.h>
#include <sys/uio.h>
#include <sys/poll.h>
#include <sys/kmem.h>
#include <sys/filio.h>
#include <sys/cmn_err.h>
#include <sys/policy.h>
#include <sys/zone.h>

#include <sys/debug.h>
#include <c2/audit.h>
#include <fs/fs_subr.h>

/*
 * Change current working directory (".").
 */
static int  chdirec(vnode_t *, int ischroot, int do_traverse);

int
chdir(char *fname)
{
    vnode_t *vp;
    int error;
    int estale_retry = 0;

lookup:
    if (error = lookupname(fname, UIO_USERSPACE, FOLLOW, NULLVPP, &vp)) {
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
            goto lookup;
        return (set_errno(error));
    }

    error = chdirec(vp, 0, 1);
    if (error) {
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
            goto lookup;
        return (set_errno(error));
    }
    return (0);
}

/*
 * File-descriptor based version of 'chdir'.
 */
int
fchdir(int fd)
{
    vnode_t *vp;
    file_t *fp;
    int error;

    if ((fp = getf(fd)) == NULL)
        return (set_errno(EBADF));
    vp = fp->f_vnode;
    VN_HOLD(vp);
    releasef(fd);
    error = chdirec(vp, 0, 0);
    if (error)
        return (set_errno(error));
    return (0);
}

/*
 * Change notion of root ("/") directory.
 */
int
chroot(char *fname)
{
    vnode_t *vp;
    int error;
    int estale_retry = 0;

lookup:
    if (error = lookupname(fname, UIO_USERSPACE, FOLLOW, NULLVPP, &vp)) {
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
            goto lookup;
        return (set_errno(error));
    }

    error = chdirec(vp, 1, 1);
    if (error) {
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
            goto lookup;
        return (set_errno(error));
    }
    return (0);
}

/*
 *  ++++++++++++++++++++++++
 *  ++  SunOS4.1 Buyback  ++
 *  ++++++++++++++++++++++++
 * Change root directory with a user given fd
 */
int
fchroot(int fd)
{
    vnode_t *vp;
    file_t *fp;
    int error;

    if ((fp = getf(fd)) == NULL)
        return (set_errno(EBADF));
    vp = fp->f_vnode;
    VN_HOLD(vp);
    releasef(fd);
    error = chdirec(vp, 1, 0);
    if (error)
        return (set_errno(error));
    return (0);
}

static int
chdirec(vnode_t *vp, int ischroot, int do_traverse)
{
    int error;
    vnode_t *oldvp;
    proc_t *pp = curproc;
    vnode_t **vpp;
    refstr_t *cwd;
    int newcwd = 1;

    if (vp->v_type != VDIR) {
        error = ENOTDIR;
        goto bad;
    }
    if (error = VOP_ACCESS(vp, VEXEC, 0, CRED(), NULL))
        goto bad;

    /*
     * The VOP_ACCESS() may have covered 'vp' with a new filesystem,
     * if 'vp' is an autoFS vnode. Traverse the mountpoint so
     * that we don't end up with a covered current directory.
     */
    if (vn_mountedvfs(vp) != NULL && do_traverse) {
        if (error = traverse(&vp))
            goto bad;
    }

    /*
     * Special chroot semantics: chroot is allowed if privileged
     * or if the target is really a loopback mount of the root (or
     * root of the zone) as determined by comparing dev and inode
     * numbers
     */
    if (ischroot) {
        struct vattr tattr;
        struct vattr rattr;
        vnode_t *zonevp = curproc->p_zone->zone_rootvp;

        tattr.va_mask = AT_FSID|AT_NODEID;
        if (error = VOP_GETATTR(vp, &tattr, 0, CRED(), NULL))
            goto bad;

        rattr.va_mask = AT_FSID|AT_NODEID;
        if (error = VOP_GETATTR(zonevp, &rattr, 0, CRED(), NULL))
            goto bad;

        if ((tattr.va_fsid != rattr.va_fsid ||
            tattr.va_nodeid != rattr.va_nodeid) &&
            (error = secpolicy_chroot(CRED())) != 0)
            goto bad;

        vpp = &PTOU(pp)->u_rdir;
    } else {
        vpp = &PTOU(pp)->u_cdir;
    }

    if (audit_active)   /* update abs cwd/root path see c2audit.c */
        audit_chdirec(vp, vpp);

    mutex_enter(&pp->p_lock);
    /*
     * This bit of logic prevents us from overwriting u_cwd if we are
     * changing to the same directory.  We set the cwd to NULL so that we
     * don't try to do the lookup on the next call to getcwd().
     */
    if (!ischroot && *vpp != NULL && vp != NULL && VN_CMP(*vpp, vp))
        newcwd = 0;

    oldvp = *vpp;
    *vpp = vp;
    if ((cwd = PTOU(pp)->u_cwd) != NULL && newcwd)
        PTOU(pp)->u_cwd = NULL;
    mutex_exit(&pp->p_lock);

    if (cwd && newcwd)
        refstr_rele(cwd);
    if (oldvp)
        VN_RELE(oldvp);
    return (0);

bad:
    VN_RELE(vp);
    return (error);
}