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 <linux/inet.h>
  22 #include "cifsglob.h"
  23 #include "cifsproto.h"
  24 #include "cifsfs.h"
  25 #include "dns_resolve.h"
  26 #include "cifs_debug.h"
  27 #include "cifs_unicode.h"
  28
  29 static LIST_HEAD(cifs_dfs_automount_list);
  30
  31 static void cifs_dfs_expire_automounts(struct work_struct *work);
  32 static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
  33                             cifs_dfs_expire_automounts);
  34 static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
  35
  36 static void cifs_dfs_expire_automounts(struct work_struct *work)
  37 {
  38         struct list_head *list = &cifs_dfs_automount_list;
  39
  40         mark_mounts_for_expiry(list);
  41         if (!list_empty(list))
  42                 schedule_delayed_work(&cifs_dfs_automount_task,
  43                                       cifs_dfs_mountpoint_expiry_timeout);
  44 }
  45
  46 void cifs_dfs_release_automount_timer(void)
  47 {
  48         BUG_ON(!list_empty(&cifs_dfs_automount_list));
  49         cancel_delayed_work_sync(&cifs_dfs_automount_task);
  50 }
  51
  52 /**
  53  * cifs_build_devname - build a devicename from a UNC and optional prepath
  54  * @nodename:   pointer to UNC string
  55  * @prepath:    pointer to prefixpath (or NULL if there isn't one)
  56  *
  57  * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
  58  * big enough to hold the final thing. Copy the UNC from the nodename, and
  59  * concatenate the prepath onto the end of it if there is one.
  60  *
  61  * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
  62  * for freeing the returned string.
  63  */
  64 static char *
  65 cifs_build_devname(char *nodename, const char *prepath)
  66 {
  67         size_t pplen;
  68         size_t unclen;
  69         char *dev;
  70         char *pos;
  71
  72         /* skip over any preceding delimiters */
  73         nodename += strspn(nodename, "\\");
  74         if (!*nodename)
  75                 return ERR_PTR(-EINVAL);
  76
  77         /* get length of UNC and set pos to last char */
  78         unclen = strlen(nodename);
  79         pos = nodename + unclen - 1;
  80
  81         /* trim off any trailing delimiters */
  82         while (*pos == '\\') {
  83                 --pos;
  84                 --unclen;
  85         }
  86
  87         /* allocate a buffer:
  88          * +2 for preceding "//"
  89          * +1 for delimiter between UNC and prepath
  90          * +1 for trailing NULL
  91          */
  92         pplen = prepath ? strlen(prepath) : 0;
  93         dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
  94         if (!dev)
  95                 return ERR_PTR(-ENOMEM);
  96
  97         pos = dev;
  98         /* add the initial "//" */
  99         *pos = '/';
 100         ++pos;
 101         *pos = '/';
 102         ++pos;
 103
 104         /* copy in the UNC portion from referral */
 105         memcpy(pos, nodename, unclen);
 106         pos += unclen;
 107
 108         /* copy the prefixpath remainder (if there is one) */
 109         if (pplen) {
 110                 *pos = '/';
 111                 ++pos;
 112                 memcpy(pos, prepath, pplen);
 113                 pos += pplen;
 114         }
 115
 116         /* NULL terminator */
 117         *pos = '\0';
 118
 119         convert_delimiter(dev, '/');
 120         return dev;
 121 }
 122
 123
 124 /**
 125  * cifs_compose_mount_options   -       creates mount options for refferral
 126  * @sb_mountdata:       parent/root DFS mount options (template)
 127  * @fullpath:           full path in UNC format
 128  * @ref:                server's referral
 129  * @devname:            pointer for saving device name
 130  *
 131  * creates mount options for submount based on template options sb_mountdata
 132  * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 133  *
 134  * Returns: pointer to new mount options or ERR_PTR.
 135  * Caller is responcible for freeing retunrned value if it is not error.
 136  */
 137 char *cifs_compose_mount_options(const char *sb_mountdata,
 138                                    const char *fullpath,
 139                                    const struct dfs_info3_param *ref,
 140                                    char **devname)
 141 {
 142         int rc;
 143         char *mountdata = NULL;
 144         const char *prepath = NULL;
 145         int md_len;
 146         char *tkn_e;
 147         char *srvIP = NULL;
 148         char sep = ',';
 149         int off, noff;
 150
 151         if (sb_mountdata == NULL)
 152                 return ERR_PTR(-EINVAL);
 153
 154         if (strlen(fullpath) - ref->path_consumed) {
 155                 prepath = fullpath + ref->path_consumed;
 156                 /* skip initial delimiter */
 157                 if (*prepath == '/' || *prepath == '\\')
 158                         prepath++;
 159         }
 160
 161         *devname = cifs_build_devname(ref->node_name, prepath);
 162         if (IS_ERR(*devname)) {
 163                 rc = PTR_ERR(*devname);
 164                 *devname = NULL;
 165                 goto compose_mount_options_err;
 166         }
 167
 168         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 169         if (rc < 0) {
 170                 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
 171                          __func__, *devname, rc);
 172                 goto compose_mount_options_err;
 173         }
 174
 175         /*
 176          * In most cases, we'll be building a shorter string than the original,
 177          * but we do have to assume that the address in the ip= option may be
 178          * much longer than the original. Add the max length of an address
 179          * string to the length of the original string to allow for worst case.
 180          */
 181         md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
 182         mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
 183         if (mountdata == NULL) {
 184                 rc = -ENOMEM;
 185                 goto compose_mount_options_err;
 186         }
 187
 188         /* copy all options except of unc,ip,prefixpath */
 189         off = 0;
 190         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 191                         sep = sb_mountdata[4];
 192                         strncpy(mountdata, sb_mountdata, 5);
 193                         off += 5;
 194         }
 195
 196         do {
 197                 tkn_e = strchr(sb_mountdata + off, sep);
 198                 if (tkn_e == NULL)
 199                         noff = strlen(sb_mountdata + off);
 200                 else
 201                         noff = tkn_e - (sb_mountdata + off) + 1;
 202
 203                 if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
 204                         off += noff;
 205                         continue;
 206                 }
 207                 if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
 208                         off += noff;
 209                         continue;
 210                 }
 211                 if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 212                         off += noff;
 213                         continue;
 214                 }
 215                 strncat(mountdata, sb_mountdata + off, noff);
 216                 off += noff;
 217         } while (tkn_e);
 218         strcat(mountdata, sb_mountdata + off);
 219         mountdata[md_len] = '\0';
 220
 221         /* copy new IP and ref share name */
 222         if (mountdata[strlen(mountdata) - 1] != sep)
 223                 strncat(mountdata, &sep, 1);
 224         strcat(mountdata, "ip=");
 225         strcat(mountdata, srvIP);
 226
 227         /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
 228         /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
 229
 230 compose_mount_options_out:
 231         kfree(srvIP);
 232         return mountdata;
 233
 234 compose_mount_options_err:
 235         kfree(mountdata);
 236         mountdata = ERR_PTR(rc);
 237         kfree(*devname);
 238         *devname = NULL;
 239         goto compose_mount_options_out;
 240 }
 241
 242 /**
 243  * cifs_dfs_do_refmount - mounts specified path using provided refferal
 244  * @cifs_sb:            parent/root superblock
 245  * @fullpath:           full path in UNC format
 246  * @ref:                server's referral
 247  */
 248 static struct vfsmount *cifs_dfs_do_refmount(struct dentry *mntpt,
 249                 struct cifs_sb_info *cifs_sb,
 250                 const char *fullpath, const struct dfs_info3_param *ref)
 251 {
 252         struct vfsmount *mnt;
 253         char *mountdata;
 254         char *devname = NULL;
 255
 256         /* strip first '\' from fullpath */
 257         mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 258                         fullpath + 1, ref, &devname);
 259
 260         if (IS_ERR(mountdata))
 261                 return (struct vfsmount *)mountdata;
 262
 263         mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
 264         kfree(mountdata);
 265         kfree(devname);
 266         return mnt;
 267
 268 }
 269
 270 static void dump_referral(const struct dfs_info3_param *ref)
 271 {
 272         cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
 273         cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
 274         cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
 275                  ref->flags, ref->server_type);
 276         cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
 277                  ref->ref_flag, ref->path_consumed);
 278 }
 279
 280 /*
 281  * Create a vfsmount that we can automount
 282  */
 283 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 284 {
 285         struct dfs_info3_param *referrals = NULL;
 286         unsigned int num_referrals = 0;
 287         struct cifs_sb_info *cifs_sb;
 288         struct cifs_ses *ses;
 289         char *full_path;
 290         unsigned int xid;
 291         int i;
 292         int rc;
 293         struct vfsmount *mnt;
 294         struct tcon_link *tlink;
 295
 296         cifs_dbg(FYI, "in %s\n", __func__);
 297         BUG_ON(IS_ROOT(mntpt));
 298
 299         /*
 300          * The MSDFS spec states that paths in DFS referral requests and
 301          * responses must be prefixed by a single '\' character instead of
 302          * the double backslashes usually used in the UNC. This function
 303          * gives us the latter, so we must adjust the result.
 304          */
 305         mnt = ERR_PTR(-ENOMEM);
 306
 307         /* always use tree name prefix */
 308         full_path = build_path_from_dentry_optional_prefix(mntpt, true);
 309         if (full_path == NULL)
 310                 goto cdda_exit;
 311
 312         cifs_sb = CIFS_SB(mntpt->d_sb);
 313         tlink = cifs_sb_tlink(cifs_sb);
 314         if (IS_ERR(tlink)) {
 315                 mnt = ERR_CAST(tlink);
 316                 goto free_full_path;
 317         }
 318         ses = tlink_tcon(tlink)->ses;
 319
 320         xid = get_xid();
 321         rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
 322                 &num_referrals, &referrals,
 323                 cifs_remap(cifs_sb));
 324         free_xid(xid);
 325
 326         cifs_put_tlink(tlink);
 327
 328         mnt = ERR_PTR(-ENOENT);
 329         for (i = 0; i < num_referrals; i++) {
 330                 int len;
 331                 dump_referral(referrals + i);
 332                 /* connect to a node */
 333                 len = strlen(referrals[i].node_name);
 334                 if (len < 2) {
 335                         cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
 336                                  __func__, referrals[i].node_name);
 337                         mnt = ERR_PTR(-EINVAL);
 338                         break;
 339                 }
 340                 mnt = cifs_dfs_do_refmount(mntpt, cifs_sb,
 341                                 full_path, referrals + i);
 342                 cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
 343                          __func__, referrals[i].node_name, mnt);
 344                 if (!IS_ERR(mnt))
 345                         goto success;
 346         }
 347
 348         /* no valid submounts were found; return error from get_dfs_path() by
 349          * preference */
 350         if (rc != 0)
 351                 mnt = ERR_PTR(rc);
 352
 353 success:
 354         free_dfs_info_array(referrals, num_referrals);
 355 free_full_path:
 356         kfree(full_path);
 357 cdda_exit:
 358         cifs_dbg(FYI, "leaving %s\n" , __func__);
 359         return mnt;
 360 }
 361
 362 /*
 363  * Attempt to automount the referral
 364  */
 365 struct vfsmount *cifs_dfs_d_automount(struct path *path)
 366 {
 367         struct vfsmount *newmnt;
 368
 369         cifs_dbg(FYI, "in %s\n", __func__);
 370
 371         newmnt = cifs_dfs_do_automount(path->dentry);
 372         if (IS_ERR(newmnt)) {
 373                 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
 374                 return newmnt;
 375         }
 376
 377         mntget(newmnt); /* prevent immediate expiration */
 378         mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
 379         schedule_delayed_work(&cifs_dfs_automount_task,
 380                               cifs_dfs_mountpoint_expiry_timeout);
 381         cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
 382         return newmnt;
 383 }
 384
 385 const struct inode_operations cifs_dfs_referral_inode_operations = {
 386 };