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 beginning 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                 cFYI(1, "%s: Failed to resolve server part of %s to IP: %d",
 145                         __func__, *devname, rc);
 146                 goto compose_mount_options_err;
 147         }
 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) + rc + strlen(ref->node_name) + 12;
 154         mountdata = kzalloc(md_len+1, GFP_KERNEL);
 155         if (mountdata == NULL) {
 156                 rc = -ENOMEM;
 157                 goto compose_mount_options_err;
 158         }
 159
 160         /* copy all options except of unc,ip,prefixpath */
 161         off = 0;
 162         if (strncmp(sb_mountdata, "sep=", 4) == 0) {
 163                         sep = sb_mountdata[4];
 164                         strncpy(mountdata, sb_mountdata, 5);
 165                         off += 5;
 166         }
 167
 168         do {
 169                 tkn_e = strchr(sb_mountdata + off, sep);
 170                 if (tkn_e == NULL)
 171                         noff = strlen(sb_mountdata + off);
 172                 else
 173                         noff = tkn_e - (sb_mountdata + off) + 1;
 174
 175                 if (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 176                         off += noff;
 177                         continue;
 178                 }
 179                 if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 180                         off += noff;
 181                         continue;
 182                 }
 183                 if (strnicmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
 184                         off += noff;
 185                         continue;
 186                 }
 187                 strncat(mountdata, sb_mountdata + off, noff);
 188                 off += noff;
 189         } while (tkn_e);
 190         strcat(mountdata, sb_mountdata + off);
 191         mountdata[md_len] = '\0';
 192
 193         /* copy new IP and ref share name */
 194         if (mountdata[strlen(mountdata) - 1] != sep)
 195                 strncat(mountdata, &sep, 1);
 196         strcat(mountdata, "ip=");
 197         strcat(mountdata, srvIP);
 198         strncat(mountdata, &sep, 1);
 199         strcat(mountdata, "unc=");
 200         strcat(mountdata, *devname);
 201
 202         /* find & copy prefixpath */
 203         tkn_e = strchr(ref->node_name + 2, '\\');
 204         if (tkn_e == NULL) {
 205                 /* invalid unc, missing share name*/
 206                 rc = -EINVAL;
 207                 goto compose_mount_options_err;
 208         }
 209
 210         tkn_e = strchr(tkn_e + 1, '\\');
 211         if (tkn_e || (strlen(fullpath) - ref->path_consumed)) {
 212                 strncat(mountdata, &sep, 1);
 213                 strcat(mountdata, "prefixpath=");
 214                 if (tkn_e)
 215                         strcat(mountdata, tkn_e + 1);
 216                 strcat(mountdata, fullpath + ref->path_consumed);
 217         }
 218
 219         /*cFYI(1, "%s: parent mountdata: %s", __func__,sb_mountdata);*/
 220         /*cFYI(1, "%s: submount mountdata: %s", __func__, mountdata );*/
 221
 222 compose_mount_options_out:
 223         kfree(srvIP);
 224         return mountdata;
 225
 226 compose_mount_options_err:
 227         kfree(mountdata);
 228         mountdata = ERR_PTR(rc);
 229         goto compose_mount_options_out;
 230 }
 231
 232 /**
 233  * cifs_dfs_do_refmount - mounts specified path using provided refferal
 234  * @cifs_sb:            parent/root superblock
 235  * @fullpath:           full path in UNC format
 236  * @ref:                server's referral
 237  */
 238 static struct vfsmount *cifs_dfs_do_refmount(struct cifs_sb_info *cifs_sb,
 239                 const char *fullpath, const struct dfs_info3_param *ref)
 240 {
 241         struct vfsmount *mnt;
 242         char *mountdata;
 243         char *devname = NULL;
 244
 245         /* strip first '\' from fullpath */
 246         mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
 247                         fullpath + 1, ref, &devname);
 248
 249         if (IS_ERR(mountdata))
 250                 return (struct vfsmount *)mountdata;
 251
 252         mnt = vfs_kern_mount(&cifs_fs_type, 0, devname, mountdata);
 253         kfree(mountdata);
 254         kfree(devname);
 255         return mnt;
 256
 257 }
 258
 259 static void dump_referral(const struct dfs_info3_param *ref)
 260 {
 261         cFYI(1, "DFS: ref path: %s", ref->path_name);
 262         cFYI(1, "DFS: node path: %s", ref->node_name);
 263         cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
 264         cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 265                                 ref->path_consumed);
 266 }
 267
 268 /*
 269  * Create a vfsmount that we can automount
 270  */
 271 static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 272 {
 273         struct dfs_info3_param *referrals = NULL;
 274         unsigned int num_referrals = 0;
 275         struct cifs_sb_info *cifs_sb;
 276         struct cifs_ses *ses;
 277         char *full_path;
 278         int xid, i;
 279         int rc;
 280         struct vfsmount *mnt;
 281         struct tcon_link *tlink;
 282
 283         cFYI(1, "in %s", __func__);
 284         BUG_ON(IS_ROOT(mntpt));
 285
 286         /*
 287          * The MSDFS spec states that paths in DFS referral requests and
 288          * responses must be prefixed by a single '\' character instead of
 289          * the double backslashes usually used in the UNC. This function
 290          * gives us the latter, so we must adjust the result.
 291          */
 292         mnt = ERR_PTR(-ENOMEM);
 293         full_path = build_path_from_dentry(mntpt);
 294         if (full_path == NULL)
 295                 goto cdda_exit;
 296
 297         cifs_sb = CIFS_SB(mntpt->d_inode->i_sb);
 298         tlink = cifs_sb_tlink(cifs_sb);
 299         if (IS_ERR(tlink)) {
 300                 mnt = ERR_CAST(tlink);
 301                 goto free_full_path;
 302         }
 303         ses = tlink_tcon(tlink)->ses;
 304
 305         xid = GetXid();
 306         rc = get_dfs_path(xid, ses, full_path + 1, cifs_sb->local_nls,
 307                 &num_referrals, &referrals,
 308                 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
 309         FreeXid(xid);
 310
 311         cifs_put_tlink(tlink);
 312
 313         mnt = ERR_PTR(-ENOENT);
 314         for (i = 0; i < num_referrals; i++) {
 315                 int len;
 316                 dump_referral(referrals + i);
 317                 /* connect to a node */
 318                 len = strlen(referrals[i].node_name);
 319                 if (len < 2) {
 320                         cERROR(1, "%s: Net Address path too short: %s",
 321                                         __func__, referrals[i].node_name);
 322                         mnt = ERR_PTR(-EINVAL);
 323                         break;
 324                 }
 325                 mnt = cifs_dfs_do_refmount(cifs_sb,
 326                                 full_path, referrals + i);
 327                 cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
 328                                         referrals[i].node_name, mnt);
 329                 if (!IS_ERR(mnt))
 330                         goto success;
 331         }
 332
 333         /* no valid submounts were found; return error from get_dfs_path() by
 334          * preference */
 335         if (rc != 0)
 336                 mnt = ERR_PTR(rc);
 337
 338 success:
 339         free_dfs_info_array(referrals, num_referrals);
 340 free_full_path:
 341         kfree(full_path);
 342 cdda_exit:
 343         cFYI(1, "leaving %s" , __func__);
 344         return mnt;
 345 }
 346
 347 /*
 348  * Attempt to automount the referral
 349  */
 350 struct vfsmount *cifs_dfs_d_automount(struct path *path)
 351 {
 352         struct vfsmount *newmnt;
 353
 354         cFYI(1, "in %s", __func__);
 355
 356         newmnt = cifs_dfs_do_automount(path->dentry);
 357         if (IS_ERR(newmnt)) {
 358                 cFYI(1, "leaving %s [automount failed]" , __func__);
 359                 return newmnt;
 360         }
 361
 362         mntget(newmnt); /* prevent immediate expiration */
 363         mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
 364         schedule_delayed_work(&cifs_dfs_automount_task,
 365                               cifs_dfs_mountpoint_expiry_timeout);
 366         cFYI(1, "leaving %s [ok]" , __func__);
 367         return newmnt;
 368 }
 369
 370 const struct inode_operations cifs_dfs_referral_inode_operations = {
 371 };