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
 157         *devname = cifs_build_devname(ref->node_name, prepath);
 158         if (IS_ERR(*devname)) {
 159                 rc = PTR_ERR(*devname);
 160                 *devname = NULL;
 161                 goto compose_mount_options_err;
 162         }
 163
 164         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 165         if (rc < 0) {
 166                 cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
 167                          __func__, *devname, rc);
 168                 goto compose_mount_options_err;
 169         }
 170
 171         /*
 172          * In most cases, we'll be building a shorter string than the original,
 173          * but we do have to assume that the address in the ip= option may be
 174          * much longer than the original. Add the max length of an address
 175          * string to the length of the original string to allow for worst case.
 176          */
 177         md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
 178         mountdata = kzalloc(md_len + 1, GFP_KERNEL);
 179         if (mountdata == NULL) {
 180                 rc = -ENOMEM;
 181                 goto compose_mount_options_err;
 182         }
 183
 184         /* copy all options except of unc,ip,prefixpath */
 185         off = 0;
 186         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 187                         sep = sb_mountdata[4];
 188                         strncpy(mountdata, sb_mountdata, 5);
 189                         off += 5;
 190         }
 191
 192         do {
 193                 tkn_e = strchr(sb_mountdata + off, sep);
 194                 if (tkn_e == NULL)
 195                         noff = strlen(sb_mountdata + off);
 196                 else
 197                         noff = tkn_e - (sb_mountdata + off) + 1;
 198
 199                 if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
 200                         off += noff;
 201                         continue;
 202                 }
 203                 if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
 204                         off += noff;
 205                         continue;
 206                 }
 207                 if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 208                         off += noff;
 209                         continue;
 210                 }
 211                 strncat(mountdata, sb_mountdata + off, noff);
 212                 off += noff;
 213         } while (tkn_e);
 214         strcat(mountdata, sb_mountdata + off);
 215         mountdata[md_len] = '\0';
 216
 217         /* copy new IP and ref share name */
 218         if (mountdata[strlen(mountdata) - 1] != sep)
 219                 strncat(mountdata, &sep, 1);
 220         strcat(mountdata, "ip=");
 221         strcat(mountdata, srvIP);
 222
 223         /*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
 224         /*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
 225
 226 compose_mount_options_out:
 227         kfree(srvIP);
 228         return mountdata;
 229
 230 compose_mount_options_err:
 231         kfree(mountdata);
 232         mountdata = ERR_PTR(rc);
 233         kfree(*devname);
 234         *devname = NULL;
 235         goto compose_mount_options_out;
 236 }
 237
 238 /**
 239  * cifs_dfs_do_refmount - mounts specified path using provided refferal
 240  * @cifs_sb:            parent/root superblock
 241  * @fullpath:           full path in UNC format
 242  * @ref:                server's referral
 243  */
 244 static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
 245                 const char *fullpath, const struct dfs_info3_param *ref)
 246 {
 247         struct vfsmount *mnt;
 248         char *mountdata;
 249         char *devname = NULL;
 250
 251         /* strip first '\' from fullpath */
 252         mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 253                         fullpath + 1, ref, &devname);
 254
 255         if (IS_ERR(mountdata))
 256                 return (struct vfsmount *)mountdata;
 257
 258         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 259         kfree(mountdata);
 260         kfree(devname);
 261         return mnt;
 262
 263 }
 264
 265 static void dump_referral(const struct dfs_info3_param *ref)
 266 {
 267         cifs_dbg(FYI, "DFS: ref path: %s\n", ref->path_name);
 268         cifs_dbg(FYI, "DFS: node path: %s\n", ref->node_name);
 269         cifs_dbg(FYI, "DFS: fl: %hd, srv_type: %hd\n",
 270                  ref->flags, ref->server_type);
 271         cifs_dbg(FYI, "DFS: ref_flags: %hd, path_consumed: %hd\n",
 272                  ref->ref_flag, ref->path_consumed);
 273 }
 274
 275 /*
 276  * Create a vfsmount that we can automount
 277  */
 278 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 279 {
 280         struct dfs_info3_param *referrals = NULL;
 281         unsigned int num_referrals = 0;
 282         struct cifs_sb_info *cifs_sb;
 283         struct cifs_ses *ses;
 284         char *full_path;
 285         unsigned int xid;
 286         int i;
 287         int rc;
 288         struct vfsmount *mnt;
 289         struct tcon_link *tlink;
 290
 291         cifs_dbg(FYI, "in %s\n", __func__);
 292         BUG_ON(IS_ROOT(mntpt));
 293
 294         /*
 295          * The MSDFS spec states that paths in DFS referral requests and
 296          * responses must be prefixed by a single '\' character instead of
 297          * the double backslashes usually used in the UNC. This function
 298          * gives us the latter, so we must adjust the result.
 299          */
 300         mnt = ERR_PTR(-ENOMEM);
 301         full_path = build_path_from_dentry(mntpt);
 302         if (full_path == NULL)
 303                 goto cdda_exit;
 304
 305         cifs_sb = CIFS_SB(d_inode(mntpt)->i_sb);
 306         tlink = cifs_sb_tlink(cifs_sb);
 307         if (IS_ERR(tlink)) {
 308                 mnt = ERR_CAST(tlink);
 309                 goto free_full_path;
 310         }
 311         ses = tlink_tcon(tlink)->ses;
 312
 313         xid = get_xid();
 314         rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
 315                 &num_referrals, &referrals,
 316                 cifs_remap(cifs_sb));
 317         free_xid(xid);
 318
 319         cifs_put_tlink(tlink);
 320
 321         mnt = ERR_PTR(-ENOENT);
 322         for (i = 0; i < num_referrals; i++) {
 323                 int len;
 324                 dump_referral(referrals + i);
 325                 /* connect to a node */
 326                 len = strlen(referrals[i].node_name);
 327                 if (len < 2) {
 328                         cifs_dbg(VFS, "%s: Net Address path too short: %s\n",
 329                                  __func__, referrals[i].node_name);
 330                         mnt = ERR_PTR(-EINVAL);
 331                         break;
 332                 }
 333                 mnt = cifs_dfs_do_refmount(cifs_sb,
 334                                 full_path, referrals + i);
 335                 cifs_dbg(FYI, "%s: cifs_dfs_do_refmount:%s , mnt:%p\n",
 336                          __func__, referrals[i].node_name, mnt);
 337                 if (!IS_ERR(mnt))
 338                         goto success;
 339         }
 340
 341         /* no valid submounts were found; return error from get_dfs_path() by
 342          * preference */
 343         if (rc != 0)
 344                 mnt = ERR_PTR(rc);
 345
 346 success:
 347         free_dfs_info_array(referrals, num_referrals);
 348 free_full_path:
 349         kfree(full_path);
 350 cdda_exit:
 351         cifs_dbg(FYI, "leaving %s\n" , __func__);
 352         return mnt;
 353 }
 354
 355 /*
 356  * Attempt to automount the referral
 357  */
 358 struct vfsmount *cifs_dfs_d_automount(struct path *path)
 359 {
 360         struct vfsmount *newmnt;
 361
 362         cifs_dbg(FYI, "in %s\n", __func__);
 363
 364         newmnt = cifs_dfs_do_automount(path->dentry);
 365         if (IS_ERR(newmnt)) {
 366                 cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
 367                 return newmnt;
 368         }
 369
 370         mntget(newmnt); /* prevent immediate expiration */
 371         mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
 372         schedule_delayed_work(&cifs_dfs_automount_task,
 373                               cifs_dfs_mountpoint_expiry_timeout);
 374         cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
 375         return newmnt;
 376 }
 377
 378 const struct inode_operations cifs_dfs_referral_inode_operations = {
 379 };