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(&cifs_dfs_automount_task);
  48         flush_scheduled_work();
  49 }
  50
  51 /**
  52  * cifs_get_share_name  -       extracts share name from UNC
  53  * @node_name:  pointer to UNC string
  54  *
  55  * Extracts sharename form full UNC.
  56  * i.e. strips from UNC trailing path that is not part of share
  57  * name and fixup missing '\' in the begining of DFS node refferal
  58  * if necessary.
  59  * Returns pointer to share name on success or ERR_PTR on error.
  60  * Caller is responsible for freeing returned string.
  61  */
  62 static char *cifs_get_share_name(const char *node_name)
  63 {
  64         int len;
  65         char *UNC;
  66         char *pSep;
  67
  68         len = strlen(node_name);
  69         UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
  70                          GFP_KERNEL);
  71         if (!UNC)
  72                 return ERR_PTR(-ENOMEM);
  73
  74         /* get share name and server name */
  75         if (node_name[1] != '\\') {
  76                 UNC[0] = '\\';
  77                 strncpy(UNC+1, node_name, len);
  78                 len++;
  79                 UNC[len] = 0;
  80         } else {
  81                 strncpy(UNC, node_name, len);
  82                 UNC[len] = 0;
  83         }
  84
  85         /* find server name end */
  86         pSep = memchr(UNC+2, '\\', len-2);
  87         if (!pSep) {
  88                 cERROR(1, "%s: no server name end in node name: %s",
  89                         __func__, node_name);
  90                 kfree(UNC);
  91                 return ERR_PTR(-EINVAL);
  92         }
  93
  94         /* find sharename end */
  95         pSep++;
  96         pSep = memchr(UNC+(pSep-UNC), '\\', len-(pSep-UNC));
  97         if (pSep) {
  98                 /* trim path up to sharename end
  99                  * now we have share name in UNC */
 100                 *pSep = 0;
 101         }
 102
 103         return UNC;
 104 }
 105
 106
 107 /**
 108  * cifs_compose_mount_options   -       creates mount options for refferral
 109  * @sb_mountdata:       parent/root DFS mount options (template)
 110  * @fullpath:           full path in UNC format
 111  * @ref:                server's referral
 112  * @devname:            pointer for saving device name
 113  *
 114  * creates mount options for submount based on template options sb_mountdata
 115  * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
 116  *
 117  * Returns: pointer to new mount options or ERR_PTR.
 118  * Caller is responcible for freeing retunrned value if it is not error.
 119  */
 120 char *cifs_compose_mount_options(const char *sb_mountdata,
 121                                    const char *fullpath,
 122                                    const struct dfs_info3_param *ref,
 123                                    char **devname)
 124 {
 125         int rc;
 126         char *mountdata = NULL;
 127         int md_len;
 128         char *tkn_e;
 129         char *srvIP = NULL;
 130         char sep = ',';
 131         int off, noff;
 132
 133         if (sb_mountdata == NULL)
 134                 return ERR_PTR(-EINVAL);
 135
 136         *devname = cifs_get_share_name(ref->node_name);
 137         if (IS_ERR(*devname)) {
 138                 rc = PTR_ERR(*devname);
 139                 *devname = NULL;
 140                 goto compose_mount_options_err;
 141         }
 142
 143         rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 144         if (rc < 0) {
 145                 cERROR(1, "%s: Failed to resolve server part of %s to IP: %d",
 146                           __func__, *devname, rc);
 147                 goto compose_mount_options_err;
 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 int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
 260                                 struct list_head *mntlist)
 261 {
 262         /* stolen from afs code */
 263         int err;
 264
 265         mntget(newmnt);
 266         err = do_add_mount(newmnt, &nd->path, nd->path.mnt->mnt_flags | MNT_SHRINKABLE, mntlist);
 267         switch (err) {
 268         case 0:
 269                 path_put(&nd->path);
 270                 nd->path.mnt = newmnt;
 271                 nd->path.dentry = dget(newmnt->mnt_root);
 272                 schedule_delayed_work(&cifs_dfs_automount_task,
 273                                       cifs_dfs_mountpoint_expiry_timeout);
 274                 break;
 275         case -EBUSY:
 276                 /* someone else made a mount here whilst we were busy */
 277                 while (d_mountpoint(nd->path.dentry) &&
 278                        follow_down(&nd->path))
 279                         ;
 280                 err = 0;
 281         default:
 282                 mntput(newmnt);
 283                 break;
 284         }
 285         return err;
 286 }
 287
 288 static void dump_referral(const struct dfs_info3_param *ref)
 289 {
 290         cFYI(1, "DFS: ref path: %s", ref->path_name);
 291         cFYI(1, "DFS: node path: %s", ref->node_name);
 292         cFYI(1, "DFS: fl: %hd, srv_type: %hd", ref->flags, ref->server_type);
 293         cFYI(1, "DFS: ref_flags: %hd, path_consumed: %hd", ref->ref_flag,
 294                                 ref->path_consumed);
 295 }
 296
 297
 298 static void*
 299 cifs_dfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 300 {
 301         struct dfs_info3_param *referrals = NULL;
 302         unsigned int num_referrals = 0;
 303         struct cifs_sb_info *cifs_sb;
 304         struct cifsSesInfo *ses;
 305         char *full_path = NULL;
 306         int xid, i;
 307         int rc = 0;
 308         struct vfsmount *mnt = ERR_PTR(-ENOENT);
 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         cifs_sb = CIFS_SB(dentry->d_inode->i_sb);
 319         ses = cifs_sb->tcon->ses;
 320
 321         if (!ses) {
 322                 rc = -EINVAL;
 323                 goto out_err;
 324         }
 325
 326         /*
 327          * The MSDFS spec states that paths in DFS referral requests and
 328          * responses must be prefixed by a single '\' character instead of
 329          * the double backslashes usually used in the UNC. This function
 330          * gives us the latter, so we must adjust the result.
 331          */
 332         full_path = build_path_from_dentry(dentry);
 333         if (full_path == NULL) {
 334                 rc = -ENOMEM;
 335                 goto out_err;
 336         }
 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         for (i = 0; i < num_referrals; i++) {
 343                 int len;
 344                 dump_referral(referrals+i);
 345                 /* connect to a node */
 346                 len = strlen(referrals[i].node_name);
 347                 if (len < 2) {
 348                         cERROR(1, "%s: Net Address path too short: %s",
 349                                         __func__, referrals[i].node_name);
 350                         rc = -EINVAL;
 351                         goto out_err;
 352                 }
 353                 mnt = cifs_dfs_do_refmount(cifs_sb,
 354                                 full_path, referrals + i);
 355                 cFYI(1, "%s: cifs_dfs_do_refmount:%s , mnt:%p", __func__,
 356                                         referrals[i].node_name, mnt);
 357
 358                 /* complete mount procedure if we accured submount */
 359                 if (!IS_ERR(mnt))
 360                         break;
 361         }
 362
 363         /* we need it cause for() above could exit without valid submount */
 364         rc = PTR_ERR(mnt);
 365         if (IS_ERR(mnt))
 366                 goto out_err;
 367
 368         rc = add_mount_helper(mnt, nd, &cifs_dfs_automount_list);
 369
 370 out:
 371         FreeXid(xid);
 372         free_dfs_info_array(referrals, num_referrals);
 373         kfree(full_path);
 374         cFYI(1, "leaving %s" , __func__);
 375         return ERR_PTR(rc);
 376 out_err:
 377         path_put(&nd->path);
 378         goto out;
 379 }
 380
 381 const struct inode_operations cifs_dfs_referral_inode_operations = {
 382         .follow_link = cifs_dfs_follow_mountpoint,
 383 };
 384