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