fs/cifs/cifs_dfs_ref.c

   1 /*
   2  *   Contains the CIFS DFS referral mounting routines used for handling
   3  *   traversal via DFS junction point
   4  *
   5  *   Copyright (c) 2007 Igor Mammedov
   6  *   Copyright (C) International Business Machines  Corp., 2008
   7  *   Author(s): Igor Mammedov (niallain@gmail.com)
   8  *              Steve French (sfrench@us.ibm.com)
   9  *   This program is free software; you can redistribute it and/or
  10  *   modify it under the terms of the GNU General Public License
  11  *   as published by the Free Software Foundation; either version
  12  *   2 of the License, or (at your option) any later version.
  13  */
  14
  15 #include <linux/dcache.h>
  16 #include <linux/mount.h>
  17 #include <linux/namei.h>
  18 #include <linux/vfs.h>
  19 #include <linux/fs.h>
  20 #include "cifsglob.h"
  21 #include "cifsproto.h"
  22 #include "cifsfs.h"
  23 #include "dns_resolve.h"
  24 #include "cifs_debug.h"
  25
  26 static LIST_HEAD(cifs_dfs_automount_list);
  27
  28 static void cifs_dfs_expire_automounts(struct work_struct *work);
  29 static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
  30                             cifs_dfs_expire_automounts);
  31 static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
  32
  33 static void cifs_dfs_expire_automounts(struct work_struct *work)
  34 {
  35         struct list_head *list = &cifs_dfs_automount_list;
  36
  37         mark_mounts_for_expiry(list);
  38         if (!list_empty(list))
  39                 schedule_delayed_work(&cifs_dfs_automount_task,
  40                                       cifs_dfs_mountpoint_expiry_timeout);
  41 }
  42
  43 void cifs_dfs_release_automount_timer(void)
  44 {
  45         BUG_ON(!list_empty(&cifs_dfs_automount_list));
  46         cancel_delayed_work(&cifs_dfs_automount_task);
  47         flush_scheduled_work();
  48 }
  49
  50 /**
  51  * cifs_get_share_name  -       extracts share name from UNC
  52  * @node_name:  pointer to UNC string
  53  *
  54  * Extracts sharename form full UNC.
  55  * i.e. strips from UNC trailing path that is not part of share
  56  * name and fixup missing '\' in the begining of DFS node refferal
  57  * if neccessary.
  58  * Returns pointer to share name on success or ERR_PTR on error.
  59  * Caller is responsible for freeing returned string.
  60  */
  61 static char *cifs_get_share_name(const char *node_name)
  62 {
  63         int len;
  64         char *UNC;
  65         char *pSep;
  66
  67         len = strlen(node_name);
  68         UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
  69                          GFP_KERNEL);
  70         if (!UNC)
  71                 return ERR_PTR(-ENOMEM);
  72
  73         /* get share name and server name */
  74         if (node_name[1] != '\\') {
  75                 UNC[0] = '\\';
  76                 strncpy(UNC+1, node_name, len);
  77                 len++;
  78                 UNC[len] = 0;
  79         } else {
  80                 strncpy(UNC, node_name, len);
  81                 UNC[len] = 0;
  82         }
  83
  84         /* find server name end */
  85         pSep = memchr(UNC+2, '\\', len-2);
  86         if (!pSep) {
  87                 cERROR(1, ("%s: no server name end in node name: %s",
  88                         __func__, node_name));
  89                 kfree(UNC);
  90                 return ERR_PTR(-EINVAL);
  91         }
  92
  93         /* find sharename end */
  94         pSep++;
  95         pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
  96         if (pSep) {
  97                 /* trim path up to sharename end
  98                  * now we have share name in UNC */
  99                 *pSep = 0;
 100         }
 101
 102         return UNC;
 103 }
 104
 105
 106 /**
 107  * cifs_compose_mount_options   -       creates mount options for refferral
 108  * @sb_mountdata:       parent/root DFS mount options (template)
 109  * @fullpath:           full path in UNC format
 110  * @ref:                server's referral
 111  * @devname:            pointer for saving device name
 112  *
 113  * creates mount options for submount based on template options sb_mountdata
 114  * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 115  *
 116  * Returns: pointer to new mount options or ERR_PTR.
 117  * Caller is responcible for freeing retunrned value if it is not error.
 118  */
 119 char *cifs_compose_mount_options(const char *sb_mountdata,
 120                                    const char *fullpath,
 121                                    const struct dfs_info3_param *ref,
 122                                    char **devname)
 123 {
 124         int rc;
 125         char *mountdata = NULL;
 126         int md_len;
 127         char *tkn_e;
 128         char *srvIP = NULL;
 129         char sep = ',';
 130         int off, noff;
 131
 132         if (sb_mountdata == NULL)
 133                 return ERR_PTR(-EINVAL);
 134
 135         *devname = cifs_get_share_name(ref->node_name);
 136         if (IS_ERR(*devname)) {
 137                 rc = PTR_ERR(*devname);
 138                 *devname = NULL;
 139                 goto compose_mount_options_err;
 140         }
 141
 142         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 143         if (rc != 0) {
 144                 cERROR(1, ("%s: Failed to resolve server part of %s to IP: %d",
 145                           __func__, *devname, rc));;
 146                 goto compose_mount_options_err;
 147         }
 148         /* md_len = strlen(...) + 12 for 'sep+prefixpath='
 149          * assuming that we have 'unc=' and 'ip=' in
 150          * the original sb_mountdata
 151          */
 152         md_len = strlen(sb_mountdata) + strlen(srvIP) +
 153                 strlen(ref->node_name) + 12;
 154         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 155         if (mountdata == NULL) {
 156                 rc = -ENOMEM;
 157                 goto compose_mount_options_err;
 158         }
 159
 160         /* copy all options except of unc,ip,prefixpath */
 161         off = 0;
 162         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 163                         sep = sb_mountdata[4];
 164                         strncpy(mountdata, sb_mountdata, 5);
 165                         off += 5;
 166         }
 167
 168         do {
 169                 tkn_e = strchr(sb_mountdata + off, sep);
 170                 if (tkn_e == NULL)
 171                         noff = strlen(sb_mountdata + off);
 172                 else
 173                         noff = tkn_e - (sb_mountdata + off) + 1;
 174
 175                 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 176                         off += noff;
 177                         continue;
 178                 }
 179                 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 180                         off += noff;
 181                         continue;
 182                 }
 183                 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 184                         off += noff;
 185                         continue;
 186                 }
 187                 strncat(mountdata, sb_mountdata + off, noff);
 188                 off += noff;
 189         } while (tkn_e);
 190         strcat(mountdata, sb_mountdata + off);
 191         mountdata[md_len] = '\0';
 192
 193         /* copy new IP and ref share name */
 194         if (mountdata[strlen(mountdata) - 1] != sep)
 195                 strncat(mountdata, &sep, 1);
 196         strcat(mountdata, "ip=");
 197         strcat(mountdata, srvIP);
 198         strncat(mountdata, &sep, 1);
 199         strcat(mountdata, "unc=");
 200         strcat(mountdata, *devname);
 201
 202         /* find & copy prefixpath */
 203         tkn_e = strchr(ref->node_name + 2, '\\');
 204         if (tkn_e == NULL) {
 205                 /* invalid unc, missing share name*/
 206                 rc = -EINVAL;
 207                 goto compose_mount_options_err;
 208         }
 209
 210         tkn_e = strchr(tkn_e + 1, '\\');
 211         if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
 212                 strncat(mountdata, &sep, 1);
 213                 strcat(mountdata, "prefixpath=");
 214                 if (tkn_e)
 215                         strcat(mountdata, tkn_e + 1);
 216                 strcat(mountdata, fullpath + ref->path_consumed);
 217         }
 218
 219         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
 220         /*cFYI(1, ("%s: submount mountdata: %s", __func__, mountdata ));*/
 221
 222 compose_mount_options_out:
 223         kfree(srvIP);
 224         return mountdata;
 225
 226 compose_mount_options_err:
 227         kfree(mountdata);
 228         mountdata = ERR_PTR(rc);
 229         goto compose_mount_options_out;
 230 }
 231
 232
 233 static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
 234                 struct dentry *dentry, const struct dfs_info3_param *ref)
 235 {
 236         struct cifs_sb_info *cifs_sb;
 237         struct vfsmount *mnt;
 238         char *mountdata;
 239         char *devname = NULL;
 240         char *fullpath;
 241
 242         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 243         /*
 244          * this function gives us a path with a double backslash prefix. We
 245          * require a single backslash for DFS.
 246          */
 247         fullpath = build_path_from_dentry(dentry);
 248         if (!fullpath)
 249                 return ERR_PTR(-ENOMEM);
 250
 251         mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 252                         fullpath + 1, ref, &devname);
 253         kfree(fullpath);
 254
 255         if (IS_ERR(mountdata))
 256                 return (struct vfsmount *)mountdata;
 257
 258         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 259         kfree(mountdata);
 260         kfree(devname);
 261         return mnt;
 262
 263 }
 264
 265 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 266                                 struct list_head *mntlist)
 267 {
 268         /* stolen from afs code */
 269         int err;
 270
 271         mntget(newmnt);
 272         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags, mntlist);
 273         switch (err) {
 274         case 0:
 275                 path_put(&nd->path);
 276                 nd->path.mnt = newmnt;
 277                 nd->path.dentry = dget(newmnt->mnt_root);
 278                 schedule_delayed_work(&cifs_dfs_automount_task,
 279                                       cifs_dfs_mountpoint_expiry_timeout);
 280                 break;
 281         case -EBUSY:
 282                 /* someone else made a mount here whilst we were busy */
 283                 while (d_mountpoint(nd->path.dentry) &&
 284                        follow_down(&nd->path))
 285                         ;
 286                 err = 0;
 287         default:
 288                 mntput(newmnt);
 289                 break;
 290         }
 291         return err;
 292 }
 293
 294 static void dump_referral(const struct dfs_info3_param *ref)
 295 {
 296         cFYI(1, ("DFS: ref path: %s", ref->path_name));
 297         cFYI(1, ("DFS: node path: %s", ref->node_name));
 298         cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
 299         cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 300                                 ref->path_consumed));
 301 }
 302
 303
 304 static void*
 305 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 306 {
 307         struct dfs_info3_param *referrals = NULL;
 308         unsigned int num_referrals = 0;
 309         struct cifs_sb_info *cifs_sb;
 310         struct cifsSesInfo *ses;
 311         char *full_path = NULL;
 312         int xid, i;
 313         int rc = 0;
 314         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 315
 316         cFYI(1, ("in %s", __func__));
 317         BUG_ON(IS_ROOT(dentry));
 318
 319         xid = GetXid();
 320
 321         dput(nd->path.dentry);
 322         nd->path.dentry = dget(dentry);
 323
 324         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 325         ses = cifs_sb->tcon->ses;
 326
 327         if (!ses) {
 328                 rc = -EINVAL;
 329                 goto out_err;
 330         }
 331
 332         /*
 333          * The MSDFS spec states that paths in DFS referral requests and
 334          * responses must be prefixed by a single '\' character instead of
 335          * the double backslashes usually used in the UNC. This function
 336          * gives us the latter, so we must adjust the result.
 337          */
 338         full_path = build_path_from_dentry(dentry);
 339         if (full_path == NULL) {
 340                 rc = -ENOMEM;
 341                 goto out_err;
 342         }
 343
 344         rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
 345                 &num_referrals, &referrals,
 346                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 347
 348         for (i = 0; i < num_referrals; i++) {
 349                 int len;
 350                 dump_referral(referrals+i);
 351                 /* connect to a node */
 352                 len = strlen(referrals[i].node_name);
 353                 if (len < 2) {
 354                         cERROR(1, ("%s: Net Address path too short: %s",
 355                                         __func__, referrals[i].node_name));
 356                         rc = -EINVAL;
 357                         goto out_err;
 358                 }
 359                 mnt = cifs_dfs_do_refmount(nd->path.mnt,
 360                                 nd->path.dentry, referrals + i);
 361                 cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
 362                                         referrals[i].node_name, mnt));
 363
 364                 /* complete mount procedure if we accured submount */
 365                 if (!IS_ERR(mnt))
 366                         break;
 367         }
 368
 369         /* we need it cause for() above could exit without valid submount */
 370         rc = PTR_ERR(mnt);
 371         if (IS_ERR(mnt))
 372                 goto out_err;
 373
 374         nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
 375         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 376
 377 out:
 378         FreeXid(xid);
 379         free_dfs_info_array(referrals, num_referrals);
 380         kfree(full_path);
 381         cFYI(1, ("leaving %s" , __func__));
 382         return ERR_PTR(rc);
 383 out_err:
 384         path_put(&nd->path);
 385         goto out;
 386 }
 387
 388 struct inode_operations cifs_dfs_referral_inode_operations = {
 389         .follow_link = cifs_dfs_follow_mountpoint,
 390 };
 391