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TOMOYO Linux Cross Reference
Linux/fs/nfs/namespace.c

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  1 /*
  2  * linux/fs/nfs/namespace.c
  3  *
  4  * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
  5  * - Modified by David Howells <dhowells@redhat.com>
  6  *
  7  * NFS namespace
  8  */
  9 
 10 #include <linux/dcache.h>
 11 #include <linux/gfp.h>
 12 #include <linux/mount.h>
 13 #include <linux/namei.h>
 14 #include <linux/nfs_fs.h>
 15 #include <linux/string.h>
 16 #include <linux/sunrpc/clnt.h>
 17 #include <linux/vfs.h>
 18 #include <linux/sunrpc/gss_api.h>
 19 #include "internal.h"
 20 
 21 #define NFSDBG_FACILITY         NFSDBG_VFS
 22 
 23 static void nfs_expire_automounts(struct work_struct *work);
 24 
 25 static LIST_HEAD(nfs_automount_list);
 26 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
 27 int nfs_mountpoint_expiry_timeout = 500 * HZ;
 28 
 29 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 30                                         struct nfs_fh *fh,
 31                                         struct nfs_fattr *fattr,
 32                                         rpc_authflavor_t authflavor);
 33 
 34 /*
 35  * nfs_path - reconstruct the path given an arbitrary dentry
 36  * @base - used to return pointer to the end of devname part of path
 37  * @dentry - pointer to dentry
 38  * @buffer - result buffer
 39  * @buflen - length of buffer
 40  *
 41  * Helper function for constructing the server pathname
 42  * by arbitrary hashed dentry.
 43  *
 44  * This is mainly for use in figuring out the path on the
 45  * server side when automounting on top of an existing partition
 46  * and in generating /proc/mounts and friends.
 47  */
 48 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
 49 {
 50         char *end;
 51         int namelen;
 52         unsigned seq;
 53         const char *base;
 54 
 55 rename_retry:
 56         end = buffer+buflen;
 57         *--end = '\0';
 58         buflen--;
 59 
 60         seq = read_seqbegin(&rename_lock);
 61         rcu_read_lock();
 62         while (1) {
 63                 spin_lock(&dentry->d_lock);
 64                 if (IS_ROOT(dentry))
 65                         break;
 66                 namelen = dentry->d_name.len;
 67                 buflen -= namelen + 1;
 68                 if (buflen < 0)
 69                         goto Elong_unlock;
 70                 end -= namelen;
 71                 memcpy(end, dentry->d_name.name, namelen);
 72                 *--end = '/';
 73                 spin_unlock(&dentry->d_lock);
 74                 dentry = dentry->d_parent;
 75         }
 76         if (read_seqretry(&rename_lock, seq)) {
 77                 spin_unlock(&dentry->d_lock);
 78                 rcu_read_unlock();
 79                 goto rename_retry;
 80         }
 81         if (*end != '/') {
 82                 if (--buflen < 0) {
 83                         spin_unlock(&dentry->d_lock);
 84                         rcu_read_unlock();
 85                         goto Elong;
 86                 }
 87                 *--end = '/';
 88         }
 89         *p = end;
 90         base = dentry->d_fsdata;
 91         if (!base) {
 92                 spin_unlock(&dentry->d_lock);
 93                 rcu_read_unlock();
 94                 WARN_ON(1);
 95                 return end;
 96         }
 97         namelen = strlen(base);
 98         /* Strip off excess slashes in base string */
 99         while (namelen > 0 && base[namelen - 1] == '/')
100                 namelen--;
101         buflen -= namelen;
102         if (buflen < 0) {
103                 spin_unlock(&dentry->d_lock);
104                 rcu_read_unlock();
105                 goto Elong;
106         }
107         end -= namelen;
108         memcpy(end, base, namelen);
109         spin_unlock(&dentry->d_lock);
110         rcu_read_unlock();
111         return end;
112 Elong_unlock:
113         spin_unlock(&dentry->d_lock);
114         rcu_read_unlock();
115         if (read_seqretry(&rename_lock, seq))
116                 goto rename_retry;
117 Elong:
118         return ERR_PTR(-ENAMETOOLONG);
119 }
120 
121 #ifdef CONFIG_NFS_V4
122 rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
123 {
124         struct gss_api_mech *mech;
125         struct xdr_netobj oid;
126         int i;
127         rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;
128 
129         for (i = 0; i < flavors->num_flavors; i++) {
130                 struct nfs4_secinfo_flavor *flavor;
131                 flavor = &flavors->flavors[i];
132 
133                 if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
134                         pseudoflavor = flavor->flavor;
135                         break;
136                 } else if (flavor->flavor == RPC_AUTH_GSS) {
137                         oid.len  = flavor->gss.sec_oid4.len;
138                         oid.data = flavor->gss.sec_oid4.data;
139                         mech = gss_mech_get_by_OID(&oid);
140                         if (!mech)
141                                 continue;
142                         pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
143                         gss_mech_put(mech);
144                         break;
145                 }
146         }
147 
148         return pseudoflavor;
149 }
150 
151 static int nfs_negotiate_security(const struct dentry *parent,
152                                   const struct dentry *dentry,
153                                   rpc_authflavor_t *flavor)
154 {
155         struct page *page;
156         struct nfs4_secinfo_flavors *flavors;
157         int (*secinfo)(struct inode *, const struct qstr *, struct nfs4_secinfo_flavors *);
158         int ret = -EPERM;
159 
160         secinfo = NFS_PROTO(parent->d_inode)->secinfo;
161         if (secinfo != NULL) {
162                 page = alloc_page(GFP_KERNEL);
163                 if (!page) {
164                         ret = -ENOMEM;
165                         goto out;
166                 }
167                 flavors = page_address(page);
168                 ret = secinfo(parent->d_inode, &dentry->d_name, flavors);
169                 *flavor = nfs_find_best_sec(flavors);
170                 put_page(page);
171         }
172 
173 out:
174         return ret;
175 }
176 
177 static int nfs_lookup_with_sec(struct nfs_server *server, struct dentry *parent,
178                                struct dentry *dentry, struct path *path,
179                                struct nfs_fh *fh, struct nfs_fattr *fattr,
180                                rpc_authflavor_t *flavor)
181 {
182         struct rpc_clnt *clone;
183         struct rpc_auth *auth;
184         int err;
185 
186         err = nfs_negotiate_security(parent, path->dentry, flavor);
187         if (err < 0)
188                 goto out;
189         clone  = rpc_clone_client(server->client);
190         auth   = rpcauth_create(*flavor, clone);
191         if (!auth) {
192                 err = -EIO;
193                 goto out_shutdown;
194         }
195         err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
196                                                   &path->dentry->d_name,
197                                                   fh, fattr);
198 out_shutdown:
199         rpc_shutdown_client(clone);
200 out:
201         return err;
202 }
203 #else /* CONFIG_NFS_V4 */
204 static inline int nfs_lookup_with_sec(struct nfs_server *server,
205                                       struct dentry *parent, struct dentry *dentry,
206                                       struct path *path, struct nfs_fh *fh,
207                                       struct nfs_fattr *fattr,
208                                       rpc_authflavor_t *flavor)
209 {
210         return -EPERM;
211 }
212 #endif /* CONFIG_NFS_V4 */
213 
214 /*
215  * nfs_d_automount - Handle crossing a mountpoint on the server
216  * @path - The mountpoint
217  *
218  * When we encounter a mountpoint on the server, we want to set up
219  * a mountpoint on the client too, to prevent inode numbers from
220  * colliding, and to allow "df" to work properly.
221  * On NFSv4, we also want to allow for the fact that different
222  * filesystems may be migrated to different servers in a failover
223  * situation, and that different filesystems may want to use
224  * different security flavours.
225  */
226 struct vfsmount *nfs_d_automount(struct path *path)
227 {
228         struct vfsmount *mnt;
229         struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
230         struct dentry *parent;
231         struct nfs_fh *fh = NULL;
232         struct nfs_fattr *fattr = NULL;
233         int err;
234         rpc_authflavor_t flavor = RPC_AUTH_UNIX;
235 
236         dprintk("--> nfs_d_automount()\n");
237 
238         mnt = ERR_PTR(-ESTALE);
239         if (IS_ROOT(path->dentry))
240                 goto out_nofree;
241 
242         mnt = ERR_PTR(-ENOMEM);
243         fh = nfs_alloc_fhandle();
244         fattr = nfs_alloc_fattr();
245         if (fh == NULL || fattr == NULL)
246                 goto out;
247 
248         dprintk("%s: enter\n", __func__);
249 
250         /* Look it up again to get its attributes */
251         parent = dget_parent(path->dentry);
252         err = server->nfs_client->rpc_ops->lookup(server->client, parent->d_inode,
253                                                   &path->dentry->d_name,
254                                                   fh, fattr);
255         if (err == -EPERM && NFS_PROTO(parent->d_inode)->secinfo != NULL)
256                 err = nfs_lookup_with_sec(server, parent, path->dentry, path, fh, fattr, &flavor);
257         dput(parent);
258         if (err != 0) {
259                 mnt = ERR_PTR(err);
260                 goto out;
261         }
262 
263         if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
264                 mnt = nfs_do_refmount(path->dentry);
265         else
266                 mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);
267         if (IS_ERR(mnt))
268                 goto out;
269 
270         dprintk("%s: done, success\n", __func__);
271         mntget(mnt); /* prevent immediate expiration */
272         mnt_set_expiry(mnt, &nfs_automount_list);
273         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
274 
275 out:
276         nfs_free_fattr(fattr);
277         nfs_free_fhandle(fh);
278 out_nofree:
279         dprintk("<-- nfs_follow_mountpoint() = %p\n", mnt);
280         return mnt;
281 }
282 
283 const struct inode_operations nfs_mountpoint_inode_operations = {
284         .getattr        = nfs_getattr,
285 };
286 
287 const struct inode_operations nfs_referral_inode_operations = {
288 };
289 
290 static void nfs_expire_automounts(struct work_struct *work)
291 {
292         struct list_head *list = &nfs_automount_list;
293 
294         mark_mounts_for_expiry(list);
295         if (!list_empty(list))
296                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
297 }
298 
299 void nfs_release_automount_timer(void)
300 {
301         if (list_empty(&nfs_automount_list))
302                 cancel_delayed_work(&nfs_automount_task);
303 }
304 
305 /*
306  * Clone a mountpoint of the appropriate type
307  */
308 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
309                                            const char *devname,
310                                            struct nfs_clone_mount *mountdata)
311 {
312 #ifdef CONFIG_NFS_V4
313         struct vfsmount *mnt = ERR_PTR(-EINVAL);
314         switch (server->nfs_client->rpc_ops->version) {
315                 case 2:
316                 case 3:
317                         mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
318                         break;
319                 case 4:
320                         mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
321         }
322         return mnt;
323 #else
324         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
325 #endif
326 }
327 
328 /**
329  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
330  * @dentry - parent directory
331  * @fh - filehandle for new root dentry
332  * @fattr - attributes for new root inode
333  * @authflavor - security flavor to use when performing the mount
334  *
335  */
336 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
337                                         struct nfs_fh *fh,
338                                         struct nfs_fattr *fattr,
339                                         rpc_authflavor_t authflavor)
340 {
341         struct nfs_clone_mount mountdata = {
342                 .sb = dentry->d_sb,
343                 .dentry = dentry,
344                 .fh = fh,
345                 .fattr = fattr,
346                 .authflavor = authflavor,
347         };
348         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
349         char *page = (char *) __get_free_page(GFP_USER);
350         char *devname;
351 
352         dprintk("--> nfs_do_submount()\n");
353 
354         dprintk("%s: submounting on %s/%s\n", __func__,
355                         dentry->d_parent->d_name.name,
356                         dentry->d_name.name);
357         if (page == NULL)
358                 goto out;
359         devname = nfs_devname(dentry, page, PAGE_SIZE);
360         mnt = (struct vfsmount *)devname;
361         if (IS_ERR(devname))
362                 goto free_page;
363         mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
364 free_page:
365         free_page((unsigned long)page);
366 out:
367         dprintk("%s: done\n", __func__);
368 
369         dprintk("<-- nfs_do_submount() = %p\n", mnt);
370         return mnt;
371 }
372 

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