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_sync(&cifs_dfs_automount_task);
  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 necessary.
  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) + rc + strlen(ref->node_name) + 12;
 153         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 154         if (mountdata == NULL) {
 155                 rc = -ENOMEM;
 156                 goto compose_mount_options_err;
 157         }
 158
 159         /* copy all options except of unc,ip,prefixpath */
 160         off = 0;
 161         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 162                         sep = sb_mountdata[4];
 163                         strncpy(mountdata, sb_mountdata, 5);
 164                         off += 5;
 165         }
 166
 167         do {
 168                 tkn_e = strchr(sb_mountdata + off, sep);
 169                 if (tkn_e == NULL)
 170                         noff = strlen(sb_mountdata + off);
 171                 else
 172                         noff = tkn_e - (sb_mountdata + off) + 1;
 173
 174                 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 175                         off += noff;
 176                         continue;
 177                 }
 178                 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 179                         off += noff;
 180                         continue;
 181                 }
 182                 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 183                         off += noff;
 184                         continue;
 185                 }
 186                 strncat(mountdata, sb_mountdata + off, noff);
 187                 off += noff;
 188         } while (tkn_e);
 189         strcat(mountdata, sb_mountdata + off);
 190         mountdata[md_len] = '\0';
 191
 192         /* copy new IP and ref share name */
 193         if (mountdata[strlen(mountdata) - 1] != sep)
 194                 strncat(mountdata, &sep, 1);
 195         strcat(mountdata, "ip=");
 196         strcat(mountdata, srvIP);
 197         strncat(mountdata, &sep, 1);
 198         strcat(mountdata, "unc=");
 199         strcat(mountdata, *devname);
 200
 201         /* find & copy prefixpath */
 202         tkn_e = strchr(ref->node_name + 2, '\\');
 203         if (tkn_e == NULL) {
 204                 /* invalid unc, missing share name*/
 205                 rc = -EINVAL;
 206                 goto compose_mount_options_err;
 207         }
 208
 209         tkn_e = strchr(tkn_e + 1, '\\');
 210         if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
 211                 strncat(mountdata, &sep, 1);
 212                 strcat(mountdata, "prefixpath=");
 213                 if (tkn_e)
 214                         strcat(mountdata, tkn_e + 1);
 215                 strcat(mountdata, fullpath + ref->path_consumed);
 216         }
 217
 218         /*cFYI(1, "%s: parent mountdata: %s", __func__,sb_mountdata);*/
 219         /*cFYI(1, "%s: submount mountdata: %s", __func__, mountdata );*/
 220
 221 compose_mount_options_out:
 222         kfree(srvIP);
 223         return mountdata;
 224
 225 compose_mount_options_err:
 226         kfree(mountdata);
 227         mountdata = ERR_PTR(rc);
 228         goto compose_mount_options_out;
 229 }
 230
 231 /**
 232  * cifs_dfs_do_refmount - mounts specified path using provided refferal
 233  * @cifs_sb:            parent/root superblock
 234  * @fullpath:           full path in UNC format
 235  * @ref:                server's referral
 236  */
 237 static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
 238                 const char *fullpath, const struct dfs_info3_param *ref)
 239 {
 240         struct vfsmount *mnt;
 241         char *mountdata;
 242         char *devname = NULL;
 243
 244         /* strip first '\' from fullpath */
 245         mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 246                         fullpath + 1, ref, &devname);
 247
 248         if (IS_ERR(mountdata))
 249                 return (struct vfsmount *)mountdata;
 250
 251         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 252         kfree(mountdata);
 253         kfree(devname);
 254         return mnt;
 255
 256 }
 257
 258 static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 259                                 struct list_head *mntlist)
 260 {
 261         /* stolen from afs code */
 262         int err;
 263
 264         mntget(newmnt);
 265         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags | MNT_SHRINKABLE, mntlist);
 266         switch (err) {
 267         case 0:
 268                 path_put(&nd->path);
 269                 nd->path.mnt = newmnt;
 270                 nd->path.dentry = dget(newmnt->mnt_root);
 271                 schedule_delayed_work(&cifs_dfs_automount_task,
 272                                       cifs_dfs_mountpoint_expiry_timeout);
 273                 break;
 274         case -EBUSY:
 275                 /* someone else made a mount here whilst we were busy */
 276                 while (d_mountpoint(nd->path.dentry) &&
 277                        follow_down(&nd->path))
 278                         ;
 279                 err = 0;
 280         default:
 281                 mntput(newmnt);
 282                 break;
 283         }
 284         return err;
 285 }
 286
 287 static void dump_referral(const struct dfs_info3_param *ref)
 288 {
 289         cFYI(1, "DFS: ref path: %s", ref->path_name);
 290         cFYI(1, "DFS: node path: %s", ref->node_name);
 291         cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
 292         cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 293                                 ref->path_consumed);
 294 }
 295
 296
 297 static void*
 298 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 299 {
 300         struct dfs_info3_param *referrals = NULL;
 301         unsigned int num_referrals = 0;
 302         struct cifs_sb_info *cifs_sb;
 303         struct cifsSesInfo *ses;
 304         char *full_path = NULL;
 305         int xid, i;
 306         int rc = 0;
 307         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 308         struct tcon_link *tlink;
 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         /*
 319          * The MSDFS spec states that paths in DFS referral requests and
 320          * responses must be prefixed by a single '\' character instead of
 321          * the double backslashes usually used in the UNC. This function
 322          * gives us the latter, so we must adjust the result.
 323          */
 324         full_path = build_path_from_dentry(dentry);
 325         if (full_path == NULL) {
 326                 rc = -ENOMEM;
 327                 goto out_err;
 328         }
 329
 330         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 331         tlink = cifs_sb_tlink(cifs_sb);
 332         if (IS_ERR(tlink)) {
 333                 rc = PTR_ERR(tlink);
 334                 goto out_err;
 335         }
 336         ses = tlink_tcon(tlink)->ses;
 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         cifs_put_tlink(tlink);
 343
 344         for (i = 0; i < num_referrals; i++) {
 345                 int len;
 346                 dump_referral(referrals+i);
 347                 /* connect to a node */
 348                 len = strlen(referrals[i].node_name);
 349                 if (len < 2) {
 350                         cERROR(1, "%s: Net Address path too short: %s",
 351                                         __func__, referrals[i].node_name);
 352                         rc = -EINVAL;
 353                         goto out_err;
 354                 }
 355                 mnt = cifs_dfs_do_refmount(cifs_sb,
 356                                 full_path, referrals + i);
 357                 cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
 358                                         referrals[i].node_name, mnt);
 359
 360                 /* complete mount procedure if we accured submount */
 361                 if (!IS_ERR(mnt))
 362                         break;
 363         }
 364
 365         /* we need it cause for() above could exit without valid submount */
 366         rc = PTR_ERR(mnt);
 367         if (IS_ERR(mnt))
 368                 goto out_err;
 369
 370         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 371
 372 out:
 373         FreeXid(xid);
 374         free_dfs_info_array(referrals, num_referrals);
 375         kfree(full_path);
 376         cFYI(1, "leaving %s" , __func__);
 377         return ERR_PTR(rc);
 378 out_err:
 379         path_put(&nd->path);
 380         goto out;
 381 }
 382
 383 const struct inode_operations cifs_dfs_referral_inode_operations = {
 384         .follow_link = cifs_dfs_follow_mountpoint,
 385 };
 386