/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1999-2001 Robert N. M. Watson
 * All rights reserved.
 *
 * This software was developed by Robert Watson for the TrustedBSD Project.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/capsicum.h>
#include <sys/lock.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/sysproto.h>
#include <sys/fcntl.h>
#include <sys/namei.h>
#include <sys/filedesc.h>
#include <sys/limits.h>
#include <sys/vnode.h>
#include <sys/proc.h>
#include <sys/extattr.h>
#include <sys/syscallsubr.h>

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

static int      user_extattr_set_path(struct thread *td, const char *path,
                    int attrnamespace, const char *attrname, void *data,
                    size_t nbytes, int follow);
static int      user_extattr_get_path(struct thread *td, const char *path,
                    int attrnamespace, const char *attrname, void *data,
                    size_t nbytes, int follow);
static int      user_extattr_delete_path(struct thread *td, const char *path,
                    int attrnamespace, const char *attrname, int follow);
static int      user_extattr_list_path(struct thread *td, const char *path,
                    int attrnamespace, void *data, size_t nbytes, int follow);

/*
 * Syscall to push extended attribute configuration information into the VFS.
 * Accepts a path, which it converts to a mountpoint, as well as a command
 * (int cmd), and attribute name and misc data.
 *
 * Currently this is used only by UFS1 extended attributes.
 */
#ifndef _SYS_SYSPROTO_H_
struct extattrctl_args {
        const char *path;
        int cmd;
        const char *filename;
        int attrnamespace;
        const char *attrname;
};
#endif
int
sys_extattrctl(struct thread *td, struct extattrctl_args *uap)
{
        struct vnode *filename_vp;
        struct nameidata nd;
        struct mount *mp, *mp_writable;
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        AUDIT_ARG_CMD(uap->cmd);
        AUDIT_ARG_VALUE(uap->attrnamespace);
        /*
         * uap->attrname is not always defined.  We check again later when we
         * invoke the VFS call so as to pass in NULL there if needed.
         */
        if (uap->attrname != NULL) {
                error = copyinstr(uap->attrname, attrname, sizeof(attrname),
                    NULL);
                if (error)
                        return (error);
        }
        AUDIT_ARG_TEXT(attrname);

        mp = NULL;
        filename_vp = NULL;
        if (uap->filename != NULL) {
                NDINIT(&nd, LOOKUP, FOLLOW | AUDITVNODE2, UIO_USERSPACE,
                    uap->filename);
                error = namei(&nd);
                if (error)
                        return (error);
                filename_vp = nd.ni_vp;
                NDFREE_PNBUF(&nd);
        }

        /* uap->path is always defined. */
        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1, UIO_USERSPACE,
            uap->path);
        error = namei(&nd);
        if (error)
                goto out;
        mp = nd.ni_vp->v_mount;
        error = vfs_busy(mp, 0);
        if (error) {
                vput(nd.ni_vp);
                NDFREE_PNBUF(&nd);
                mp = NULL;
                goto out;
        }
        VOP_UNLOCK(nd.ni_vp);
        error = vn_start_write(nd.ni_vp, &mp_writable, V_WAIT | V_PCATCH);
        vrele(nd.ni_vp);
        NDFREE_PNBUF(&nd);
        if (error)
                goto out;
        if (filename_vp != NULL) {
                /*
                 * uap->filename is not always defined.  If it is,
                 * grab a vnode lock, which VFS_EXTATTRCTL() will
                 * later release.
                 */
                error = vn_lock(filename_vp, LK_EXCLUSIVE);
                if (error) {
                        vn_finished_write(mp_writable);
                        goto out;
                }
        }

        error = VFS_EXTATTRCTL(mp, uap->cmd, filename_vp, uap->attrnamespace,
            uap->attrname != NULL ? attrname : NULL);

        vn_finished_write(mp_writable);
out:
        if (mp != NULL)
                vfs_unbusy(mp);

        /*
         * VFS_EXTATTRCTL will have unlocked, but not de-ref'd, filename_vp,
         * so vrele it if it is defined.
         */
        if (filename_vp != NULL)
                vrele(filename_vp);
        return (error);
}

/*-
 * Set a named extended attribute on a file or directory
 *
 * Arguments: unlocked vnode "vp", attribute namespace "attrnamespace",
 *            kernelspace string pointer "attrname", userspace buffer
 *            pointer "data", buffer length "nbytes", thread "td".
 * Returns: 0 on success, an error number otherwise
 * Locks: none
 * References: vp must be a valid reference for the duration of the call
 */
static int
extattr_set_vp(struct vnode *vp, int attrnamespace, const char *attrname,
    void *data, size_t nbytes, struct thread *td)
{
        struct mount *mp;
        struct uio auio;
        struct iovec aiov;
        ssize_t cnt;
        int error;

        if (nbytes > IOSIZE_MAX)
                return (EINVAL);

        error = vn_start_write(vp, &mp, V_WAIT | V_PCATCH);
        if (error)
                return (error);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);

        aiov.iov_base = data;
        aiov.iov_len = nbytes;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_offset = 0;
        auio.uio_resid = nbytes;
        auio.uio_rw = UIO_WRITE;
        auio.uio_segflg = UIO_USERSPACE;
        auio.uio_td = td;
        cnt = nbytes;

#ifdef MAC
        error = mac_vnode_check_setextattr(td->td_ucred, vp, attrnamespace,
            attrname);
        if (error)
                goto done;
#endif

        error = VOP_SETEXTATTR(vp, attrnamespace, attrname, &auio,
            td->td_ucred, td);
        cnt -= auio.uio_resid;
        td->td_retval[0] = cnt;

#ifdef MAC
done:
#endif
        VOP_UNLOCK(vp);
        vn_finished_write(mp);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_set_fd_args {
        int fd;
        int attrnamespace;
        const char *attrname;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_set_fd(struct thread *td, struct extattr_set_fd_args *uap)
{
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        error = copyinstr(uap->attrname, attrname, sizeof(attrname), NULL);
        if (error)
                return (error);
        return (kern_extattr_set_fd(td, uap->fd, uap->attrnamespace,
            attrname, uap->data, uap->nbytes));
}

int
kern_extattr_set_fd(struct thread *td, int fd, int attrnamespace,
    const char *attrname, void *data, size_t nbytes)
{
        struct file *fp;
        cap_rights_t rights;
        int error;

        AUDIT_ARG_FD(fd);
        AUDIT_ARG_VALUE(attrnamespace);
        AUDIT_ARG_TEXT(attrname);

        error = getvnode_path(td, fd,
            cap_rights_init_one(&rights, CAP_EXTATTR_SET), NULL, &fp);
        if (error)
                return (error);

        error = extattr_set_vp(fp->f_vnode, attrnamespace,
            attrname, data, nbytes, td);
        fdrop(fp, td);

        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_set_file_args {
        const char *path;
        int attrnamespace;
        const char *attrname;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_set_file(struct thread *td, struct extattr_set_file_args *uap)
{

        return (user_extattr_set_path(td, uap->path, uap->attrnamespace,
            uap->attrname, uap->data, uap->nbytes, FOLLOW));
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_set_link_args {
        const char *path;
        int attrnamespace;
        const char *attrname;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_set_link(struct thread *td, struct extattr_set_link_args *uap)
{

        return (user_extattr_set_path(td, uap->path, uap->attrnamespace,
            uap->attrname, uap->data, uap->nbytes, NOFOLLOW));
}

static int
user_extattr_set_path(struct thread *td, const char *path, int attrnamespace,
    const char *uattrname, void *data, size_t nbytes, int follow)
{
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        error = copyinstr(uattrname, attrname, sizeof(attrname), NULL);
        if (error)
                return (error);
        return (kern_extattr_set_path(td, path, attrnamespace,
            attrname, data, nbytes, follow, UIO_USERSPACE));
}

int
kern_extattr_set_path(struct thread *td, const char *path, int attrnamespace,
    const char *attrname, void *data, size_t nbytes, int follow,
    enum uio_seg pathseg)
{
        struct nameidata nd;
        int error;

        AUDIT_ARG_VALUE(attrnamespace);
        AUDIT_ARG_TEXT(attrname);

        NDINIT(&nd, LOOKUP, follow | AUDITVNODE1, pathseg, path);
        error = namei(&nd);
        if (error)
                return (error);
        NDFREE_PNBUF(&nd);

        error = extattr_set_vp(nd.ni_vp, attrnamespace, attrname, data,
            nbytes, td);

        vrele(nd.ni_vp);
        return (error);
}

/*-
 * Get a named extended attribute on a file or directory
 *
 * Arguments: unlocked vnode "vp", attribute namespace "attrnamespace",
 *            kernelspace string pointer "attrname", userspace buffer
 *            pointer "data", buffer length "nbytes", thread "td".
 * Returns: 0 on success, an error number otherwise
 * Locks: none
 * References: vp must be a valid reference for the duration of the call
 */
static int
extattr_get_vp(struct vnode *vp, int attrnamespace, const char *attrname,
    void *data, size_t nbytes, struct thread *td)
{
        struct uio auio, *auiop;
        struct iovec aiov;
        ssize_t cnt;
        size_t size, *sizep;
        int error;

        if (nbytes > IOSIZE_MAX)
                return (EINVAL);

        vn_lock(vp, LK_SHARED | LK_RETRY);

        /*
         * Slightly unusual semantics: if the user provides a NULL data
         * pointer, they don't want to receive the data, just the maximum
         * read length.
         */
        auiop = NULL;
        sizep = NULL;
        cnt = 0;
        if (data != NULL) {
                aiov.iov_base = data;
                aiov.iov_len = nbytes;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = 0;
                auio.uio_resid = nbytes;
                auio.uio_rw = UIO_READ;
                auio.uio_segflg = UIO_USERSPACE;
                auio.uio_td = td;
                auiop = &auio;
                cnt = nbytes;
        } else
                sizep = &size;

#ifdef MAC
        error = mac_vnode_check_getextattr(td->td_ucred, vp, attrnamespace,
            attrname);
        if (error)
                goto done;
#endif

        error = VOP_GETEXTATTR(vp, attrnamespace, attrname, auiop, sizep,
            td->td_ucred, td);

        if (auiop != NULL) {
                cnt -= auio.uio_resid;
                td->td_retval[0] = cnt;
        } else
                td->td_retval[0] = size;
#ifdef MAC
done:
#endif
        VOP_UNLOCK(vp);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_get_fd_args {
        int fd;
        int attrnamespace;
        const char *attrname;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_get_fd(struct thread *td, struct extattr_get_fd_args *uap)
{
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        error = copyinstr(uap->attrname, attrname, sizeof(attrname), NULL);
        if (error)
                return (error);
        return (kern_extattr_get_fd(td, uap->fd, uap->attrnamespace,
            attrname, uap->data, uap->nbytes));
}

int
kern_extattr_get_fd(struct thread *td, int fd, int attrnamespace,
    const char *attrname, void *data, size_t nbytes)
{
        struct file *fp;
        cap_rights_t rights;
        int error;

        AUDIT_ARG_FD(fd);
        AUDIT_ARG_VALUE(attrnamespace);
        AUDIT_ARG_TEXT(attrname);

        error = getvnode_path(td, fd,
            cap_rights_init_one(&rights, CAP_EXTATTR_GET), NULL, &fp);
        if (error)
                return (error);

        error = extattr_get_vp(fp->f_vnode, attrnamespace,
            attrname, data, nbytes, td);

        fdrop(fp, td);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_get_file_args {
        const char *path;
        int attrnamespace;
        const char *attrname;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_get_file(struct thread *td, struct extattr_get_file_args *uap)
{
        return (user_extattr_get_path(td, uap->path, uap->attrnamespace,
            uap->attrname, uap->data, uap->nbytes, FOLLOW));
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_get_link_args {
        const char *path;
        int attrnamespace;
        const char *attrname;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_get_link(struct thread *td, struct extattr_get_link_args *uap)
{
        return (user_extattr_get_path(td, uap->path, uap->attrnamespace,
            uap->attrname, uap->data, uap->nbytes, NOFOLLOW));
}

static int
user_extattr_get_path(struct thread *td, const char *path, int attrnamespace,
    const char *uattrname, void *data, size_t nbytes, int follow)
{
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        error = copyinstr(uattrname, attrname, sizeof(attrname), NULL);
        if (error)
                return (error);
        return (kern_extattr_get_path(td, path, attrnamespace,
            attrname, data, nbytes, follow, UIO_USERSPACE));
}

int
kern_extattr_get_path(struct thread *td, const char *path, int attrnamespace,
    const char *attrname, void *data, size_t nbytes, int follow,
    enum uio_seg pathseg)
{
        struct nameidata nd;
        int error;

        AUDIT_ARG_VALUE(attrnamespace);
        AUDIT_ARG_TEXT(attrname);

        NDINIT(&nd, LOOKUP, follow | AUDITVNODE1, pathseg, path);
        error = namei(&nd);
        if (error)
                return (error);
        NDFREE_PNBUF(&nd);

        error = extattr_get_vp(nd.ni_vp, attrnamespace, attrname, data,
            nbytes, td);

        vrele(nd.ni_vp);
        return (error);
}

/*
 * extattr_delete_vp(): Delete a named extended attribute on a file or
 *                      directory
 *
 * Arguments: unlocked vnode "vp", attribute namespace "attrnamespace",
 *            kernelspace string pointer "attrname", proc "p"
 * Returns: 0 on success, an error number otherwise
 * Locks: none
 * References: vp must be a valid reference for the duration of the call
 */
static int
extattr_delete_vp(struct vnode *vp, int attrnamespace, const char *attrname,
    struct thread *td)
{
        struct mount *mp;
        int error;

        error = vn_start_write(vp, &mp, V_WAIT | V_PCATCH);
        if (error)
                return (error);
        vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);

#ifdef MAC
        error = mac_vnode_check_deleteextattr(td->td_ucred, vp, attrnamespace,
            attrname);
        if (error)
                goto done;
#endif

        error = VOP_DELETEEXTATTR(vp, attrnamespace, attrname, td->td_ucred,
            td);
        if (error == EOPNOTSUPP)
                error = VOP_SETEXTATTR(vp, attrnamespace, attrname, NULL,
                    td->td_ucred, td);
#ifdef MAC
done:
#endif
        VOP_UNLOCK(vp);
        vn_finished_write(mp);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_delete_fd_args {
        int fd;
        int attrnamespace;
        const char *attrname;
};
#endif
int
sys_extattr_delete_fd(struct thread *td, struct extattr_delete_fd_args *uap)
{
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        error = copyinstr(uap->attrname, attrname, sizeof(attrname), NULL);
        if (error)
                return (error);
        return (kern_extattr_delete_fd(td, uap->fd, uap->attrnamespace,
            attrname));
}

int
kern_extattr_delete_fd(struct thread *td, int fd, int attrnamespace,
    const char *attrname)
{
        struct file *fp;
        cap_rights_t rights;
        int error;

        AUDIT_ARG_FD(fd);
        AUDIT_ARG_VALUE(attrnamespace);
        AUDIT_ARG_TEXT(attrname);

        error = getvnode_path(td, fd,
            cap_rights_init_one(&rights, CAP_EXTATTR_DELETE), NULL, &fp);
        if (error)
                return (error);

        error = extattr_delete_vp(fp->f_vnode, attrnamespace,
            attrname, td);
        fdrop(fp, td);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_delete_file_args {
        const char *path;
        int attrnamespace;
        const char *attrname;
};
#endif
int
sys_extattr_delete_file(struct thread *td, struct extattr_delete_file_args *uap)
{

        return (user_extattr_delete_path(td, uap->path, uap->attrnamespace,
            uap->attrname, FOLLOW));
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_delete_link_args {
        const char *path;
        int attrnamespace;
        const char *attrname;
};
#endif
int
sys_extattr_delete_link(struct thread *td, struct extattr_delete_link_args *uap)
{

        return (user_extattr_delete_path(td, uap->path, uap->attrnamespace,
            uap->attrname, NOFOLLOW));
}

int
user_extattr_delete_path(struct thread *td, const char *path, int attrnamespace,
    const char *uattrname, int follow)
{
        char attrname[EXTATTR_MAXNAMELEN + 1];
        int error;

        error = copyinstr(uattrname, attrname, sizeof(attrname), NULL);
        if (error)
                return(error);
        return (kern_extattr_delete_path(td, path, attrnamespace,
            attrname, follow, UIO_USERSPACE));
}

int
kern_extattr_delete_path(struct thread *td, const char *path, int attrnamespace,
    const char *attrname, int follow, enum uio_seg pathseg)
{
        struct nameidata nd;
        int error;

        AUDIT_ARG_VALUE(attrnamespace);
        AUDIT_ARG_TEXT(attrname);

        NDINIT(&nd, LOOKUP, follow | AUDITVNODE1, pathseg, path);
        error = namei(&nd);
        if (error)
                return(error);
        NDFREE_PNBUF(&nd);

        error = extattr_delete_vp(nd.ni_vp, attrnamespace, attrname, td);
        vrele(nd.ni_vp);
        return(error);
}

/*-
 * Retrieve a list of extended attributes on a file or directory.
 *
 * Arguments: unlocked vnode "vp", attribute namespace 'attrnamespace",
 *            userspace buffer pointer "data", buffer length "nbytes",
 *            thread "td".
 * Returns: 0 on success, an error number otherwise
 * Locks: none
 * References: vp must be a valid reference for the duration of the call
 */
static int
extattr_list_vp(struct vnode *vp, int attrnamespace, struct uio *auiop,
    struct thread *td)
{
        size_t size, *sizep;
        ssize_t cnt;
        int error;

        sizep = NULL;
        cnt = 0;
        if (auiop != NULL) {
                if (auiop->uio_resid > IOSIZE_MAX)
                        return (EINVAL);
                cnt = auiop->uio_resid;
        } else
                sizep = &size;

        vn_lock(vp, LK_SHARED | LK_RETRY);

#ifdef MAC
        error = mac_vnode_check_listextattr(td->td_ucred, vp, attrnamespace);
        if (error) {
                VOP_UNLOCK(vp);
                return (error);
        }
#endif

        error = VOP_LISTEXTATTR(vp, attrnamespace, auiop, sizep,
            td->td_ucred, td);
        VOP_UNLOCK(vp);

        if (auiop != NULL) {
                cnt -= auiop->uio_resid;
                td->td_retval[0] = cnt;
        } else
                td->td_retval[0] = size;
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_list_fd_args {
        int fd;
        int attrnamespace;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_list_fd(struct thread *td, struct extattr_list_fd_args *uap)
{
        struct uio auio, *auiop;
        struct iovec aiov;

        if (uap->data != NULL) {
                aiov.iov_base = uap->data;
                aiov.iov_len = uap->nbytes;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = 0;
                auio.uio_resid = uap->nbytes;
                auio.uio_rw = UIO_READ;
                auio.uio_segflg = UIO_USERSPACE;
                auio.uio_td = td;
                auiop = &auio;
        } else
                auiop = NULL;

        return (kern_extattr_list_fd(td, uap->fd, uap->attrnamespace,
            auiop));
}

int
kern_extattr_list_fd(struct thread *td, int fd, int attrnamespace,
    struct uio *auiop)
{
        struct file *fp;
        cap_rights_t rights;
        int error;

        AUDIT_ARG_FD(fd);
        AUDIT_ARG_VALUE(attrnamespace);
        error = getvnode_path(td, fd,
            cap_rights_init_one(&rights, CAP_EXTATTR_LIST), NULL, &fp);
        if (error)
                return (error);

        error = extattr_list_vp(fp->f_vnode, attrnamespace, auiop, td);

        fdrop(fp, td);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_list_file_args {
        const char *path;
        int attrnamespace;
        void *data;
        size_t nbytes;
}
#endif
int
sys_extattr_list_file(struct thread *td, struct extattr_list_file_args *uap)
{

        return (user_extattr_list_path(td, uap->path, uap->attrnamespace,
            uap->data, uap->nbytes, FOLLOW));
}

#ifndef _SYS_SYSPROTO_H_
struct extattr_list_link_args {
        const char *path;
        int attrnamespace;
        void *data;
        size_t nbytes;
};
#endif
int
sys_extattr_list_link(struct thread *td, struct extattr_list_link_args *uap)
{

        return (user_extattr_list_path(td, uap->path, uap->attrnamespace,
            uap->data, uap->nbytes, NOFOLLOW));
}

static int
user_extattr_list_path(struct thread *td, const char *path, int attrnamespace,
    void *data, size_t nbytes, int follow)
{
        struct uio auio, *auiop;
        struct iovec aiov;

        if (data != NULL) {
                aiov.iov_base = data;
                aiov.iov_len = nbytes;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = 0;
                auio.uio_resid = nbytes;
                auio.uio_rw = UIO_READ;
                auio.uio_segflg = UIO_USERSPACE;
                auio.uio_td = td;
                auiop = &auio;
        } else
                auiop = NULL;

        return (kern_extattr_list_path(td, path, attrnamespace,
            auiop, follow, UIO_USERSPACE));
}

int
kern_extattr_list_path(struct thread *td, const char *path, int attrnamespace,
    struct uio *auiop, int follow, enum uio_seg pathseg)
{
        struct nameidata nd;
        int error;

        AUDIT_ARG_VALUE(attrnamespace);
        NDINIT(&nd, LOOKUP, follow | AUDITVNODE1, pathseg, path);
        error = namei(&nd);
        if (error)
                return (error);
        NDFREE_PNBUF(&nd);

        error = extattr_list_vp(nd.ni_vp, attrnamespace, auiop, td);

        vrele(nd.ni_vp);
        return (error);
}