fs/smb/client/dfs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2022 Paulo Alcantara <[email protected]>
   4  */
   5
   6 #include "cifsproto.h"
   7 #include "cifs_debug.h"
   8 #include "dns_resolve.h"
   9 #include "fs_context.h"
  10 #include "dfs.h"
  11
  12 /**
  13  * dfs_parse_target_referral - set fs context for dfs target referral
  14  *
  15  * @full_path: full path in UNC format.
  16  * @ref: dfs referral pointer.
  17  * @ctx: smb3 fs context pointer.
  18  *
  19  * Return zero if dfs referral was parsed correctly, otherwise non-zero.
  20  */
  21 int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
  22                               struct smb3_fs_context *ctx)
  23 {
  24         int rc;
  25         const char *prepath = NULL;
  26         char *path;
  27
  28         if (!full_path || !*full_path || !ref || !ctx)
  29                 return -EINVAL;
  30
  31         if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
  32                 return -EINVAL;
  33
  34         if (strlen(full_path) - ref->path_consumed) {
  35                 prepath = full_path + ref->path_consumed;
  36                 /* skip initial delimiter */
  37                 if (*prepath == '/' || *prepath == '\\')
  38                         prepath++;
  39         }
  40
  41         path = cifs_build_devname(ref->node_name, prepath);
  42         if (IS_ERR(path))
  43                 return PTR_ERR(path);
  44
  45         rc = smb3_parse_devname(path, ctx);
  46         if (rc)
  47                 goto out;
  48
  49         rc = dns_resolve_server_name_to_ip(path, (struct sockaddr *)&ctx->dstaddr, NULL);
  50
  51 out:
  52         kfree(path);
  53         return rc;
  54 }
  55
  56 static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
  57 {
  58         struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
  59         int rc;
  60
  61         ctx->leaf_fullpath = (char *)full_path;
  62         rc = cifs_mount_get_session(mnt_ctx);
  63         ctx->leaf_fullpath = NULL;
  64
  65         return rc;
  66 }
  67
  68 /*
  69  * Get an active reference of @ses so that next call to cifs_put_tcon() won't
  70  * release it as any new DFS referrals must go through its IPC tcon.
  71  */
  72 static void set_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
  73 {
  74         struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
  75         struct cifs_ses *ses = mnt_ctx->ses;
  76
  77         if (ses) {
  78                 spin_lock(&cifs_tcp_ses_lock);
  79                 cifs_smb_ses_inc_refcount(ses);
  80                 spin_unlock(&cifs_tcp_ses_lock);
  81         }
  82         ctx->dfs_root_ses = ses;
  83 }
  84
  85 static inline int parse_dfs_target(struct smb3_fs_context *ctx,
  86                                    struct dfs_ref_walk *rw,
  87                                    struct dfs_info3_param *tgt)
  88 {
  89         int rc;
  90         const char *fpath = ref_walk_fpath(rw) + 1;
  91
  92         rc = ref_walk_get_tgt(rw, tgt);
  93         if (!rc)
  94                 rc = dfs_parse_target_referral(fpath, tgt, ctx);
  95         return rc;
  96 }
  97
  98 static int setup_dfs_ref(struct cifs_mount_ctx *mnt_ctx,
  99                          struct dfs_info3_param *tgt,
 100                          struct dfs_ref_walk *rw)
 101 {
 102         struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 103         struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
 104         char *ref_path, *full_path;
 105         int rc;
 106
 107         full_path = smb3_fs_context_fullpath(ctx, CIFS_DIR_SEP(cifs_sb));
 108         if (IS_ERR(full_path))
 109                 return PTR_ERR(full_path);
 110
 111         if (!tgt || (tgt->server_type == DFS_TYPE_LINK &&
 112                      DFS_INTERLINK(tgt->flags)))
 113                 ref_path = dfs_get_path(cifs_sb, ctx->UNC);
 114         else
 115                 ref_path = dfs_get_path(cifs_sb, full_path);
 116         if (IS_ERR(ref_path)) {
 117                 rc = PTR_ERR(ref_path);
 118                 kfree(full_path);
 119                 return rc;
 120         }
 121         ref_walk_path(rw) = ref_path;
 122         ref_walk_fpath(rw) = full_path;
 123         ref_walk_ses(rw) = ctx->dfs_root_ses;
 124         return 0;
 125 }
 126
 127 static int __dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
 128                                struct dfs_ref_walk *rw)
 129 {
 130         struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 131         struct dfs_info3_param tgt = {};
 132         int rc = -ENOENT;
 133
 134 again:
 135         do {
 136                 ctx->dfs_root_ses = ref_walk_ses(rw);
 137                 if (ref_walk_empty(rw)) {
 138                         rc = dfs_get_referral(mnt_ctx, ref_walk_path(rw) + 1,
 139                                               NULL, ref_walk_tl(rw));
 140                         if (rc) {
 141                                 rc = cifs_mount_get_tcon(mnt_ctx);
 142                                 if (!rc)
 143                                         rc = cifs_is_path_remote(mnt_ctx);
 144                                 continue;
 145                         }
 146                         if (!ref_walk_num_tgts(rw)) {
 147                                 rc = -ENOENT;
 148                                 continue;
 149                         }
 150                 }
 151
 152                 while (ref_walk_next_tgt(rw)) {
 153                         rc = parse_dfs_target(ctx, rw, &tgt);
 154                         if (rc)
 155                                 continue;
 156
 157                         cifs_mount_put_conns(mnt_ctx);
 158                         rc = get_session(mnt_ctx, ref_walk_path(rw));
 159                         if (rc)
 160                                 continue;
 161
 162                         ref_walk_set_tgt_hint(rw);
 163                         if (tgt.flags & DFSREF_STORAGE_SERVER) {
 164                                 rc = cifs_mount_get_tcon(mnt_ctx);
 165                                 if (!rc)
 166                                         rc = cifs_is_path_remote(mnt_ctx);
 167                                 if (!rc)
 168                                         break;
 169                                 if (rc != -EREMOTE)
 170                                         continue;
 171                         }
 172
 173                         set_root_smb_session(mnt_ctx);
 174                         rc = ref_walk_advance(rw);
 175                         if (!rc) {
 176                                 rc = setup_dfs_ref(mnt_ctx, &tgt, rw);
 177                                 if (!rc) {
 178                                         rc = -EREMOTE;
 179                                         goto again;
 180                                 }
 181                         }
 182                         if (rc != -ELOOP)
 183                                 goto out;
 184                 }
 185         } while (rc && ref_walk_descend(rw));
 186
 187 out:
 188         free_dfs_info_param(&tgt);
 189         return rc;
 190 }
 191
 192 static int dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
 193                              struct dfs_ref_walk **rw)
 194 {
 195         int rc;
 196
 197         *rw = ref_walk_alloc();
 198         if (IS_ERR(*rw)) {
 199                 rc = PTR_ERR(*rw);
 200                 *rw = NULL;
 201                 return rc;
 202         }
 203
 204         ref_walk_init(*rw);
 205         rc = setup_dfs_ref(mnt_ctx, NULL, *rw);
 206         if (!rc)
 207                 rc = __dfs_referral_walk(mnt_ctx, *rw);
 208         return rc;
 209 }
 210
 211 static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 212 {
 213         struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
 214         struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 215         struct dfs_ref_walk *rw = NULL;
 216         struct cifs_tcon *tcon;
 217         char *origin_fullpath;
 218         int rc;
 219
 220         origin_fullpath = dfs_get_path(cifs_sb, ctx->source);
 221         if (IS_ERR(origin_fullpath))
 222                 return PTR_ERR(origin_fullpath);
 223
 224         rc = dfs_referral_walk(mnt_ctx, &rw);
 225         if (!rc) {
 226                 /*
 227                  * Prevent superblock from being created with any missing
 228                  * connections.
 229                  */
 230                 if (WARN_ON(!mnt_ctx->server))
 231                         rc = -EHOSTDOWN;
 232                 else if (WARN_ON(!mnt_ctx->ses))
 233                         rc = -EACCES;
 234                 else if (WARN_ON(!mnt_ctx->tcon))
 235                         rc = -ENOENT;
 236         }
 237         if (rc)
 238                 goto out;
 239
 240         tcon = mnt_ctx->tcon;
 241         spin_lock(&tcon->tc_lock);
 242         tcon->origin_fullpath = origin_fullpath;
 243         origin_fullpath = NULL;
 244         ref_walk_set_tcon(rw, tcon);
 245         spin_unlock(&tcon->tc_lock);
 246         queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
 247                            dfs_cache_get_ttl() * HZ);
 248
 249 out:
 250         kfree(origin_fullpath);
 251         ref_walk_free(rw);
 252         return rc;
 253 }
 254
 255 /*
 256  * If @ctx->dfs_automount, then update @ctx->dstaddr earlier with the DFS root
 257  * server from where we'll start following any referrals.  Otherwise rely on the
 258  * value provided by mount(2) as the user might not have dns_resolver key set up
 259  * and therefore failing to upcall to resolve UNC hostname under @ctx->source.
 260  */
 261 static int update_fs_context_dstaddr(struct smb3_fs_context *ctx)
 262 {
 263         struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
 264         int rc = 0;
 265
 266         if (!ctx->nodfs && ctx->dfs_automount) {
 267                 rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);
 268                 if (!rc)
 269                         cifs_set_port(addr, ctx->port);
 270                 ctx->dfs_automount = false;
 271         }
 272         return rc;
 273 }
 274
 275 int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
 276 {
 277         struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
 278         bool nodfs = ctx->nodfs;
 279         int rc;
 280
 281         rc = update_fs_context_dstaddr(ctx);
 282         if (rc)
 283                 return rc;
 284
 285         rc = get_session(mnt_ctx, NULL);
 286         if (rc)
 287                 return rc;
 288
 289         /*
 290          * If called with 'nodfs' mount option, then skip DFS resolving.  Otherwise unconditionally
 291          * try to get an DFS referral (even cached) to determine whether it is an DFS mount.
 292          *
 293          * Skip prefix path to provide support for DFS referrals from w2k8 servers which don't seem
 294          * to respond with PATH_NOT_COVERED to requests that include the prefix.
 295          */
 296         if (!nodfs) {
 297                 rc = dfs_get_referral(mnt_ctx, ctx->UNC + 1, NULL, NULL);
 298                 if (rc) {
 299                         cifs_dbg(FYI, "%s: no dfs referral for %s: %d\n",
 300                                  __func__, ctx->UNC + 1, rc);
 301                         cifs_dbg(FYI, "%s: assuming non-dfs mount...\n", __func__);
 302                         nodfs = true;
 303                 }
 304         }
 305         if (nodfs) {
 306                 rc = cifs_mount_get_tcon(mnt_ctx);
 307                 if (!rc)
 308                         rc = cifs_is_path_remote(mnt_ctx);
 309                 return rc;
 310         }
 311
 312         if (!ctx->dfs_conn) {
 313                 ctx->dfs_conn = true;
 314                 cifs_mount_put_conns(mnt_ctx);
 315                 rc = get_session(mnt_ctx, NULL);
 316         }
 317         if (!rc) {
 318                 set_root_smb_session(mnt_ctx);
 319                 rc = __dfs_mount_share(mnt_ctx);
 320         }
 321         return rc;
 322 }
 323
 324 static int target_share_matches_server(struct TCP_Server_Info *server, char *share,
 325                                        bool *target_match)
 326 {
 327         int rc = 0;
 328         const char *dfs_host;
 329         size_t dfs_host_len;
 330
 331         *target_match = true;
 332         extract_unc_hostname(share, &dfs_host, &dfs_host_len);
 333
 334         /* Check if hostnames or addresses match */
 335         cifs_server_lock(server);
 336         if (dfs_host_len != strlen(server->hostname) ||
 337             strncasecmp(dfs_host, server->hostname, dfs_host_len)) {
 338                 cifs_dbg(FYI, "%s: %.*s doesn't match %s\n", __func__,
 339                          (int)dfs_host_len, dfs_host, server->hostname);
 340                 rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
 341                 if (rc)
 342                         cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
 343         }
 344         cifs_server_unlock(server);
 345         return rc;
 346 }
 347
 348 static int tree_connect_dfs_target(const unsigned int xid,
 349                                    struct cifs_tcon *tcon,
 350                                    struct cifs_sb_info *cifs_sb,
 351                                    char *tree, bool islink,
 352                                    struct dfs_cache_tgt_list *tl)
 353 {
 354         const struct smb_version_operations *ops = tcon->ses->server->ops;
 355         struct TCP_Server_Info *server = tcon->ses->server;
 356         struct dfs_cache_tgt_iterator *tit;
 357         char *share = NULL, *prefix = NULL;
 358         bool target_match;
 359         int rc = -ENOENT;
 360
 361         /* Try to tree connect to all dfs targets */
 362         for (tit = dfs_cache_get_tgt_iterator(tl);
 363              tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
 364                 kfree(share);
 365                 kfree(prefix);
 366                 share = prefix = NULL;
 367
 368                 /* Check if share matches with tcp ses */
 369                 rc = dfs_cache_get_tgt_share(server->leaf_fullpath + 1, tit, &share, &prefix);
 370                 if (rc) {
 371                         cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
 372                         break;
 373                 }
 374
 375                 rc = target_share_matches_server(server, share, &target_match);
 376                 if (rc)
 377                         break;
 378                 if (!target_match) {
 379                         rc = -EHOSTUNREACH;
 380                         continue;
 381                 }
 382
 383                 dfs_cache_noreq_update_tgthint(server->leaf_fullpath + 1, tit);
 384                 scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
 385                 rc = ops->tree_connect(xid, tcon->ses, tree,
 386                                        tcon, tcon->ses->local_nls);
 387                 if (islink && !rc && cifs_sb)
 388                         rc = cifs_update_super_prepath(cifs_sb, prefix);
 389                 break;
 390         }
 391
 392         kfree(share);
 393         kfree(prefix);
 394         dfs_cache_free_tgts(tl);
 395         return rc;
 396 }
 397
 398 int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon)
 399 {
 400         int rc;
 401         struct TCP_Server_Info *server = tcon->ses->server;
 402         const struct smb_version_operations *ops = server->ops;
 403         DFS_CACHE_TGT_LIST(tl);
 404         struct cifs_sb_info *cifs_sb = NULL;
 405         struct super_block *sb = NULL;
 406         struct dfs_info3_param ref = {0};
 407         char *tree;
 408
 409         /* only send once per connect */
 410         spin_lock(&tcon->tc_lock);
 411
 412         /* if tcon is marked for needing reconnect, update state */
 413         if (tcon->need_reconnect)
 414                 tcon->status = TID_NEED_TCON;
 415
 416         if (tcon->status == TID_GOOD) {
 417                 spin_unlock(&tcon->tc_lock);
 418                 return 0;
 419         }
 420
 421         if (tcon->status != TID_NEW &&
 422             tcon->status != TID_NEED_TCON) {
 423                 spin_unlock(&tcon->tc_lock);
 424                 return -EHOSTDOWN;
 425         }
 426
 427         tcon->status = TID_IN_TCON;
 428         spin_unlock(&tcon->tc_lock);
 429
 430         tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
 431         if (!tree) {
 432                 rc = -ENOMEM;
 433                 goto out;
 434         }
 435
 436         if (tcon->ipc) {
 437                 cifs_server_lock(server);
 438                 scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
 439                 cifs_server_unlock(server);
 440                 rc = ops->tree_connect(xid, tcon->ses, tree,
 441                                        tcon, tcon->ses->local_nls);
 442                 goto out;
 443         }
 444
 445         sb = cifs_get_dfs_tcon_super(tcon);
 446         if (!IS_ERR(sb))
 447                 cifs_sb = CIFS_SB(sb);
 448
 449         /* Tree connect to last share in @tcon->tree_name if no DFS referral */
 450         if (!server->leaf_fullpath ||
 451             dfs_cache_noreq_find(server->leaf_fullpath + 1, &ref, &tl)) {
 452                 rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name,
 453                                        tcon, tcon->ses->local_nls);
 454                 goto out;
 455         }
 456
 457         rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
 458                                      &tl);
 459         free_dfs_info_param(&ref);
 460
 461 out:
 462         kfree(tree);
 463         cifs_put_tcp_super(sb);
 464
 465         if (rc) {
 466                 spin_lock(&tcon->tc_lock);
 467                 if (tcon->status == TID_IN_TCON)
 468                         tcon->status = TID_NEED_TCON;
 469                 spin_unlock(&tcon->tc_lock);
 470         } else {
 471                 spin_lock(&tcon->tc_lock);
 472                 if (tcon->status == TID_IN_TCON)
 473                         tcon->status = TID_GOOD;
 474                 tcon->need_reconnect = false;
 475                 spin_unlock(&tcon->tc_lock);
 476         }
 477
 478         return rc;
 479 }