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![Latchesar Ionkov](/assets/img/avatar_default.png)
The 9P2000 protocol requires the authentication and permission checks to be done in the file server. For that reason every user that accesses the file server tree has to authenticate and attach to the server separately. Multiple users can share the same connection to the server. Currently v9fs does a single attach and executes all I/O operations as a single user. This makes using v9fs in multiuser environment unsafe as it depends on the client doing the permission checking. This patch improves the 9P2000 support by allowing every user to attach separately. The patch defines three modes of access (new mount option 'access'): - attach-per-user (access=user) (default mode for 9P2000.u) If a user tries to access a file served by v9fs for the first time, v9fs sends an attach command to the server (Tattach) specifying the user. If the attach succeeds, the user can access the v9fs tree. As there is no uname->uid (string->integer) mapping yet, this mode works only with the 9P2000.u dialect. - allow only one user to access the tree (access=<uid>) Only the user with uid can access the v9fs tree. Other users that attempt to access it will get EPERM error. - do all operations as a single user (access=any) (default for 9P2000) V9fs does a single attach and all operations are done as a single user. If this mode is selected, the v9fs behavior is identical with the current one. Signed-off-by: Latchesar Ionkov <lucho@ionkov.net> Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
210 lines
4.6 KiB
C
210 lines
4.6 KiB
C
/*
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* V9FS FID Management
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*
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* Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
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* Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to:
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* Free Software Foundation
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02111-1301 USA
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*
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*/
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#include <linux/module.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/idr.h>
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#include <asm/semaphore.h>
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#include <net/9p/9p.h>
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#include <net/9p/client.h>
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#include "v9fs.h"
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#include "v9fs_vfs.h"
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#include "fid.h"
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/**
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* v9fs_fid_add - add a fid to a dentry
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* @dentry: dentry that the fid is being added to
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* @fid: fid to add
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*
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*/
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int v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
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{
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struct v9fs_dentry *dent;
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P9_DPRINTK(P9_DEBUG_VFS, "fid %d dentry %s\n",
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fid->fid, dentry->d_iname);
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dent = dentry->d_fsdata;
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if (!dent) {
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dent = kmalloc(sizeof(struct v9fs_dentry), GFP_KERNEL);
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if (!dent)
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return -ENOMEM;
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spin_lock_init(&dent->lock);
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INIT_LIST_HEAD(&dent->fidlist);
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dentry->d_fsdata = dent;
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}
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spin_lock(&dent->lock);
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list_add(&fid->dlist, &dent->fidlist);
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spin_unlock(&dent->lock);
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return 0;
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}
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/**
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* v9fs_fid_find - retrieve a fid that belongs to the specified uid
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* @dentry: dentry to look for fid in
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* @uid: return fid that belongs to the specified user
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* @any: if non-zero, return any fid associated with the dentry
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*
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*/
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static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any)
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{
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struct v9fs_dentry *dent;
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struct p9_fid *fid, *ret;
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P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p) uid %d any %d\n",
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dentry->d_iname, dentry, uid, any);
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dent = (struct v9fs_dentry *) dentry->d_fsdata;
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ret = NULL;
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if (dent) {
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spin_lock(&dent->lock);
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list_for_each_entry(fid, &dent->fidlist, dlist) {
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if (any || fid->uid == uid) {
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ret = fid;
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break;
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}
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}
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spin_unlock(&dent->lock);
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}
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return ret;
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}
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/**
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* v9fs_fid_lookup - lookup for a fid, try to walk if not found
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* @dentry: dentry to look for fid in
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*
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* Look for a fid in the specified dentry for the current user.
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* If no fid is found, try to create one walking from a fid from the parent
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* dentry (if it has one), or the root dentry. If the user haven't accessed
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* the fs yet, attach now and walk from the root.
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*/
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struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
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{
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int i, n, l, clone, any, access;
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u32 uid;
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struct p9_fid *fid;
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struct dentry *d, *ds;
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struct v9fs_session_info *v9ses;
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char **wnames, *uname;
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v9ses = v9fs_inode2v9ses(dentry->d_inode);
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access = v9ses->flags & V9FS_ACCESS_MASK;
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switch (access) {
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case V9FS_ACCESS_SINGLE:
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case V9FS_ACCESS_USER:
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uid = current->fsuid;
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any = 0;
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break;
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case V9FS_ACCESS_ANY:
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uid = v9ses->uid;
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any = 1;
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break;
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default:
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uid = ~0;
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any = 0;
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break;
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}
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fid = v9fs_fid_find(dentry, uid, any);
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if (fid)
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return fid;
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ds = dentry->d_parent;
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fid = v9fs_fid_find(ds, uid, any);
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if (!fid) { /* walk from the root */
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n = 0;
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for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
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n++;
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fid = v9fs_fid_find(ds, uid, any);
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if (!fid) { /* the user is not attached to the fs yet */
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if (access == V9FS_ACCESS_SINGLE)
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return ERR_PTR(-EPERM);
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if (v9fs_extended(v9ses))
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uname = NULL;
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else
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uname = v9ses->uname;
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fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
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v9ses->aname);
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if (IS_ERR(fid))
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return fid;
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v9fs_fid_add(ds, fid);
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}
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} else /* walk from the parent */
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n = 1;
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if (ds == dentry)
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return fid;
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wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
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if (!wnames)
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return ERR_PTR(-ENOMEM);
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for (d = dentry, i = n; i >= 0; i--, d = d->d_parent)
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wnames[i] = (char *) d->d_name.name;
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clone = 1;
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i = 0;
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while (i < n) {
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l = min(n - i, P9_MAXWELEM);
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fid = p9_client_walk(fid, l, &wnames[i], clone);
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if (!fid) {
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kfree(wnames);
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return fid;
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}
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i += l;
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clone = 0;
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}
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kfree(wnames);
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v9fs_fid_add(dentry, fid);
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return fid;
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}
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struct p9_fid *v9fs_fid_clone(struct dentry *dentry)
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{
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struct p9_fid *fid, *ret;
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fid = v9fs_fid_lookup(dentry);
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if (IS_ERR(fid))
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return fid;
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ret = p9_client_walk(fid, 0, NULL, 1);
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return ret;
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}
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