linux/fs/cifs/cifs_dfs_ref.c
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   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
  28static LIST_HEAD(cifs_dfs_automount_list);
  29
  30static void cifs_dfs_expire_automounts(struct work_struct *work);
  31static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
  32                            cifs_dfs_expire_automounts);
  33static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
  34
  35static 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
  45void 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 */
  63static char *
  64cifs_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 */
 136char *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 (strnicmp(sb_mountdata + off, "unc=", 4) == 0) {
 199                        off += noff;
 200                        continue;
 201                }
 202                if (strnicmp(sb_mountdata + off, "ip=", 3) == 0) {
 203                        off += noff;
 204                        continue;
 205                }
 206                if (strnicmp(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
 225compose_mount_options_out:
 226        kfree(srvIP);
 227        return mountdata;
 228
 229compose_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 */
 243static 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
 264static 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 */
 277static 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
 345success:
 346        free_dfs_info_array(referrals, num_referrals);
 347free_full_path:
 348        kfree(full_path);
 349cdda_exit:
 350        cifs_dbg(FYI, "leaving %s\n" , __func__);
 351        return mnt;
 352}
 353
 354/*
 355 * Attempt to automount the referral
 356 */
 357struct 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
 377const struct inode_operations cifs_dfs_referral_inode_operations = {
 378};
 379
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