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