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 NULL 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 NULL;
  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 NULL;
  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         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 137         if (rc != 0) {
 138                 cERROR(1, ("%s: Failed to resolve server part of %s to IP: %d",
 139                           __func__, *devname, rc));;
 140                 goto compose_mount_options_err;
 141         }
 142         /* md_len = strlen(...) + 12 for 'sep+prefixpath='
 143          * assuming that we have 'unc=' and 'ip=' in
 144          * the original sb_mountdata
 145          */
 146         md_len = strlen(sb_mountdata) + strlen(srvIP) +
 147                 strlen(ref->node_name) + 12;
 148         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 149         if (mountdata == NULL) {
 150                 rc = -ENOMEM;
 151                 goto compose_mount_options_err;
 152         }
 153
 154         /* copy all options except of unc,ip,prefixpath */
 155         off = 0;
 156         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 157                         sep = sb_mountdata[4];
 158                         strncpy(mountdata, sb_mountdata, 5);
 159                         off += 5;
 160         }
 161
 162         do {
 163                 tkn_e = strchr(sb_mountdata + off, sep);
 164                 if (tkn_e == NULL)
 165                         noff = strlen(sb_mountdata + off);
 166                 else
 167                         noff = tkn_e - (sb_mountdata + off) + 1;
 168
 169                 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 170                         off += noff;
 171                         continue;
 172                 }
 173                 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 174                         off += noff;
 175                         continue;
 176                 }
 177                 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 178                         off += noff;
 179                         continue;
 180                 }
 181                 strncat(mountdata, sb_mountdata + off, noff);
 182                 off += noff;
 183         } while (tkn_e);
 184         strcat(mountdata, sb_mountdata + off);
 185         mountdata[md_len] = '\0';
 186
 187         /* copy new IP and ref share name */
 188         if (mountdata[strlen(mountdata) - 1] != sep)
 189                 strncat(mountdata, &sep, 1);
 190         strcat(mountdata, "ip=");
 191         strcat(mountdata, srvIP);
 192         strncat(mountdata, &sep, 1);
 193         strcat(mountdata, "unc=");
 194         strcat(mountdata, *devname);
 195
 196         /* find & copy prefixpath */
 197         tkn_e = strchr(ref->node_name + 2, '\\');
 198         if (tkn_e == NULL) {
 199                 /* invalid unc, missing share name*/
 200                 rc = -EINVAL;
 201                 goto compose_mount_options_err;
 202         }
 203
 204         tkn_e = strchr(tkn_e + 1, '\\');
 205         if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
 206                 strncat(mountdata, &sep, 1);
 207                 strcat(mountdata, "prefixpath=");
 208                 if (tkn_e)
 209                         strcat(mountdata, tkn_e + 1);
 210                 strcat(mountdata, fullpath + ref->path_consumed);
 211         }
 212
 213         /*cFYI(1,("%s: parent mountdata: %s", __func__,sb_mountdata));*/
 214         /*cFYI(1, ("%s: submount mountdata: %s", __func__, mountdata ));*/
 215
 216 compose_mount_options_out:
 217         kfree(srvIP);
 218         return mountdata;
 219
 220 compose_mount_options_err:
 221         kfree(mountdata);
 222         mountdata = ERR_PTR(rc);
 223         goto compose_mount_options_out;
 224 }
 225
 226
 227 static struct vfsmount *cifs_dfs_do_refmount(const struct vfsmount *mnt_parent,
 228                 struct dentry *dentry, const struct dfs_info3_param *ref)
 229 {
 230         struct cifs_sb_info *cifs_sb;
 231         struct vfsmount *mnt;
 232         char *mountdata;
 233         char *devname = NULL;
 234         char *fullpath;
 235
 236         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 237         /*
 238          * this function gives us a path with a double backslash prefix. We
 239          * require a single backslash for DFS.
 240          */
 241         fullpath = build_path_from_dentry(dentry);
 242         if (!fullpath)
 243                 return ERR_PTR(-ENOMEM);
 244
 245         mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 246                         fullpath + 1, ref, &devname);
 247         kfree(fullpath);
 248
 249         if (IS_ERR(mountdata))
 250                 return (struct vfsmount *)mountdata;
 251
 252         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 253         kfree(mountdata);
 254         kfree(devname);
 255         return mnt;
 256
 257 }
 258
 259 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 260                                 struct list_head *mntlist)
 261 {
 262         /* stolen from afs code */
 263         int err;
 264
 265         mntget(newmnt);
 266         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags, mntlist);
 267         switch (err) {
 268         case 0:
 269                 path_put(&nd->path);
 270                 nd->path.mnt = newmnt;
 271                 nd->path.dentry = dget(newmnt->mnt_root);
 272                 schedule_delayed_work(&cifs_dfs_automount_task,
 273                                       cifs_dfs_mountpoint_expiry_timeout);
 274                 break;
 275         case -EBUSY:
 276                 /* someone else made a mount here whilst we were busy */
 277                 while (d_mountpoint(nd->path.dentry) &&
 278                        follow_down(&nd->path))
 279                         ;
 280                 err = 0;
 281         default:
 282                 mntput(newmnt);
 283                 break;
 284         }
 285         return err;
 286 }
 287
 288 static void dump_referral(const struct dfs_info3_param *ref)
 289 {
 290         cFYI(1, ("DFS: ref path: %s", ref->path_name));
 291         cFYI(1, ("DFS: node path: %s", ref->node_name));
 292         cFYI(1, ("DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type));
 293         cFYI(1, ("DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 294                                 ref->path_consumed));
 295 }
 296
 297
 298 static void*
 299 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 300 {
 301         struct dfs_info3_param *referrals = NULL;
 302         unsigned int num_referrals = 0;
 303         struct cifs_sb_info *cifs_sb;
 304         struct cifsSesInfo *ses;
 305         char *full_path = NULL;
 306         int xid, i;
 307         int rc = 0;
 308         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 309
 310         cFYI(1, ("in %s", __func__));
 311         BUG_ON(IS_ROOT(dentry));
 312
 313         xid = GetXid();
 314
 315         dput(nd->path.dentry);
 316         nd->path.dentry = dget(dentry);
 317
 318         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 319         ses = cifs_sb->tcon->ses;
 320
 321         if (!ses) {
 322                 rc = -EINVAL;
 323                 goto out_err;
 324         }
 325
 326         /*
 327          * The MSDFS spec states that paths in DFS referral requests and
 328          * responses must be prefixed by a single '\' character instead of
 329          * the double backslashes usually used in the UNC. This function
 330          * gives us the latter, so we must adjust the result.
 331          */
 332         full_path = build_path_from_dentry(dentry);
 333         if (full_path == NULL) {
 334                 rc = -ENOMEM;
 335                 goto out_err;
 336         }
 337
 338         rc = get_dfs_path(xid, ses , full_path + 1, cifs_sb->local_nls,
 339                 &num_referrals, &referrals,
 340                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 341
 342         for (i = 0; i < num_referrals; i++) {
 343                 int len;
 344                 dump_referral(referrals+i);
 345                 /* connect to a node */
 346                 len = strlen(referrals[i].node_name);
 347                 if (len < 2) {
 348                         cERROR(1, ("%s: Net Address path too short: %s",
 349                                         __func__, referrals[i].node_name));
 350                         rc = -EINVAL;
 351                         goto out_err;
 352                 }
 353                 mnt = cifs_dfs_do_refmount(nd->path.mnt,
 354                                 nd->path.dentry, referrals + i);
 355                 cFYI(1, ("%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
 356                                         referrals[i].node_name, mnt));
 357
 358                 /* complete mount procedure if we accured submount */
 359                 if (!IS_ERR(mnt))
 360                         break;
 361         }
 362
 363         /* we need it cause for() above could exit without valid submount */
 364         rc = PTR_ERR(mnt);
 365         if (IS_ERR(mnt))
 366                 goto out_err;
 367
 368         nd->path.mnt->mnt_flags |= MNT_SHRINKABLE;
 369         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 370
 371 out:
 372         FreeXid(xid);
 373         free_dfs_info_array(referrals, num_referrals);
 374         kfree(full_path);
 375         cFYI(1, ("leaving %s" , __func__));
 376         return ERR_PTR(rc);
 377 out_err:
 378         path_put(&nd->path);
 379         goto out;
 380 }
 381
 382 struct inode_operations cifs_dfs_referral_inode_operations = {
 383         .follow_link = cifs_dfs_follow_mountpoint,
 384 };
 385