Merge tag '5.9-rc-smb3-fixes-part1' of git://git.samba.org/sfrench/cifs-2.6

Pull cifs updates from Steve French:
 "16 cifs/smb3 fixes, about half DFS related, two fixes for stable.

  Still working on and testing an additional set of fixes (including
  updates to mount, and some fallocate scenario improvements) for later
  in the merge window"

* tag '5.9-rc-smb3-fixes-part1' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: document and cleanup dfs mount
  cifs: only update prefix path of DFS links in cifs_tree_connect()
  cifs: fix double free error on share and prefix
  cifs: handle RESP_GET_DFS_REFERRAL.PathConsumed in reconnect
  cifs: handle empty list of targets in cifs_reconnect()
  cifs: rename reconn_inval_dfs_target()
  cifs: reduce number of referral requests in DFS link lookups
  cifs: merge __{cifs,smb2}_reconnect[_tcon]() into cifs_tree_connect()
  cifs: convert to use be32_add_cpu()
  cifs: delete duplicated words in header files
  cifs: Remove the superfluous break
  cifs: smb1: Try failing back to SetFileInfo if SetPathInfo fails
  cifs`: handle ERRBaduid for SMB1
  cifs: remove unused variable 'server'
  smb3: warn on confusing error scenario with sec=krb5
  cifs: Fix leak when handling lease break for cached root fid

1 files changed, 307 insertions, 201 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index a61abde09ffe..7e3e5e2098eb 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -393,15 +393,14 @@ static inline int reconn_set_ipaddr(struct TCP_Server_Info *server)
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
 /* These functions must be called with server->srv_mutex held */
-static void reconn_inval_dfs_target(struct TCP_Server_Info *server,
-				    struct cifs_sb_info *cifs_sb,
-				    struct dfs_cache_tgt_list *tgt_list,
-				    struct dfs_cache_tgt_iterator **tgt_it)
+static void reconn_set_next_dfs_target(struct TCP_Server_Info *server,
+				       struct cifs_sb_info *cifs_sb,
+				       struct dfs_cache_tgt_list *tgt_list,
+				       struct dfs_cache_tgt_iterator **tgt_it)
 {
 	const char *name;
 
-	if (!cifs_sb || !cifs_sb->origin_fullpath || !tgt_list ||
-	    !server->nr_targets)
+	if (!cifs_sb || !cifs_sb->origin_fullpath)
 		return;
 
 	if (!*tgt_it) {
@@ -471,11 +470,13 @@ cifs_reconnect(struct TCP_Server_Info *server)
 		sb = NULL;
 	} else {
 		cifs_sb = CIFS_SB(sb);
-
 		rc = reconn_setup_dfs_targets(cifs_sb, &tgt_list);
-		if (rc && (rc != -EOPNOTSUPP)) {
-			cifs_server_dbg(VFS, "%s: no target servers for DFS failover\n",
-				 __func__);
+		if (rc) {
+			cifs_sb = NULL;
+			if (rc != -EOPNOTSUPP) {
+				cifs_server_dbg(VFS, "%s: no target servers for DFS failover\n",
+						__func__);
+			}
 		} else {
 			server->nr_targets = dfs_cache_get_nr_tgts(&tgt_list);
 		}
@@ -578,7 +579,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 		 * feature is disabled, then we will retry last server we
 		 * connected to before.
 		 */
-		reconn_inval_dfs_target(server, cifs_sb, &tgt_list, &tgt_it);
+		reconn_set_next_dfs_target(server, cifs_sb, &tgt_list, &tgt_it);
 #endif
 		rc = reconn_set_ipaddr(server);
 		if (rc) {
@@ -4422,11 +4423,11 @@ build_unc_path_to_root(const struct smb_vol *vol,
 static int
 expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
 		    struct smb_vol *volume_info, struct cifs_sb_info *cifs_sb,
-		    int check_prefix)
+		    char *ref_path)
 {
 	int rc;
 	struct dfs_info3_param referral = {0};
-	char *full_path = NULL, *ref_path = NULL, *mdata = NULL;
+	char *full_path = NULL, *mdata = NULL;
 
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
 		return -EREMOTE;
@@ -4435,9 +4436,6 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
 	if (IS_ERR(full_path))
 		return PTR_ERR(full_path);
 
-	/* For DFS paths, skip the first '\' of the UNC */
-	ref_path = check_prefix ? full_path + 1 : volume_info->UNC + 1;
-
 	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
 			    ref_path, &referral, NULL);
 	if (!rc) {
@@ -4500,13 +4498,10 @@ static int update_vol_info(const struct dfs_cache_tgt_iterator *tgt_it,
 	return 0;
 }
 
-static int setup_dfs_tgt_conn(const char *path,
+static int setup_dfs_tgt_conn(const char *path, const char *full_path,
 			      const struct dfs_cache_tgt_iterator *tgt_it,
-			      struct cifs_sb_info *cifs_sb,
-			      struct smb_vol *vol,
-			      unsigned int *xid,
-			      struct TCP_Server_Info **server,
-			      struct cifs_ses **ses,
+			      struct cifs_sb_info *cifs_sb, struct smb_vol *vol, unsigned int *xid,
+			      struct TCP_Server_Info **server, struct cifs_ses **ses,
 			      struct cifs_tcon **tcon)
 {
 	int rc;
@@ -4520,8 +4515,7 @@ static int setup_dfs_tgt_conn(const char *path,
 	if (rc)
 		return rc;
 
-	mdata = cifs_compose_mount_options(cifs_sb->mountdata, path, &ref,
-					   &fake_devname);
+	mdata = cifs_compose_mount_options(cifs_sb->mountdata, full_path + 1, &ref, &fake_devname);
 	free_dfs_info_param(&ref);
 
 	if (IS_ERR(mdata)) {
@@ -4544,7 +4538,7 @@ static int setup_dfs_tgt_conn(const char *path,
 		mount_put_conns(cifs_sb, *xid, *server, *ses, *tcon);
 		rc = mount_get_conns(&fake_vol, cifs_sb, xid, server, ses,
 				     tcon);
-		if (!rc) {
+		if (!rc || (*server && *ses)) {
 			/*
 			 * We were able to connect to new target server.
 			 * Update current volume info with new target server.
@@ -4556,14 +4550,10 @@ static int setup_dfs_tgt_conn(const char *path,
 	return rc;
 }
 
-static int mount_do_dfs_failover(const char *path,
-				 struct cifs_sb_info *cifs_sb,
-				 struct smb_vol *vol,
-				 struct cifs_ses *root_ses,
-				 unsigned int *xid,
-				 struct TCP_Server_Info **server,
-				 struct cifs_ses **ses,
-				 struct cifs_tcon **tcon)
+static int do_dfs_failover(const char *path, const char *full_path, struct cifs_sb_info *cifs_sb,
+			   struct smb_vol *vol, struct cifs_ses *root_ses, unsigned int *xid,
+			   struct TCP_Server_Info **server, struct cifs_ses **ses,
+			   struct cifs_tcon **tcon)
 {
 	int rc;
 	struct dfs_cache_tgt_list tgt_list;
@@ -4582,9 +4572,9 @@ static int mount_do_dfs_failover(const char *path,
 		if (rc)
 			break;
 		/* Connect to next DFS target */
-		rc = setup_dfs_tgt_conn(path, tgt_it, cifs_sb, vol, xid, server,
-					ses, tcon);
-		if (!rc || rc == -EACCES || rc == -EOPNOTSUPP)
+		rc = setup_dfs_tgt_conn(path, full_path, tgt_it, cifs_sb, vol, xid, server, ses,
+					tcon);
+		if (!rc || (*server && *ses))
 			break;
 	}
 	if (!rc) {
@@ -4754,207 +4744,210 @@ static int is_path_remote(struct cifs_sb_info *cifs_sb, struct smb_vol *vol,
 }
 
 #ifdef CONFIG_CIFS_DFS_UPCALL
-static inline void set_root_tcon(struct cifs_sb_info *cifs_sb,
-				 struct cifs_tcon *tcon,
-				 struct cifs_tcon **root)
+static void set_root_ses(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
+			 struct cifs_ses **root_ses)
 {
-	spin_lock(&cifs_tcp_ses_lock);
-	tcon->tc_count++;
-	tcon->remap = cifs_remap(cifs_sb);
-	spin_unlock(&cifs_tcp_ses_lock);
-	*root = tcon;
+	if (ses) {
+		spin_lock(&cifs_tcp_ses_lock);
+		ses->ses_count++;
+		ses->tcon_ipc->remap = cifs_remap(cifs_sb);
+		spin_unlock(&cifs_tcp_ses_lock);
+	}
+	*root_ses = ses;
+}
+
+static void put_root_ses(struct cifs_ses *ses)
+{
+	if (ses)
+		cifs_put_smb_ses(ses);
+}
+
+/* Check if a path component is remote and then update @dfs_path accordingly */
+static int check_dfs_prepath(struct cifs_sb_info *cifs_sb, struct smb_vol *vol,
+			     const unsigned int xid, struct TCP_Server_Info *server,
+			     struct cifs_tcon *tcon, char **dfs_path)
+{
+	char *path, *s;
+	char sep = CIFS_DIR_SEP(cifs_sb), tmp;
+	char *npath;
+	int rc = 0;
+	int added_treename = tcon->Flags & SMB_SHARE_IS_IN_DFS;
+	int skip = added_treename;
+
+	path = cifs_build_path_to_root(vol, cifs_sb, tcon, added_treename);
+	if (!path)
+		return -ENOMEM;
+
+	/*
+	 * Walk through the path components in @path and check if they're accessible. In case any of
+	 * the components is -EREMOTE, then update @dfs_path with the next DFS referral request path
+	 * (NOT including the remaining components).
+	 */
+	s = path;
+	do {
+		/* skip separators */
+		while (*s && *s == sep)
+			s++;
+		if (!*s)
+			break;
+		/* next separator */
+		while (*s && *s != sep)
+			s++;
+		/*
+		 * if the treename is added, we then have to skip the first
+		 * part within the separators
+		 */
+		if (skip) {
+			skip = 0;
+			continue;
+		}
+		tmp = *s;
+		*s = 0;
+		rc = server->ops->is_path_accessible(xid, tcon, cifs_sb, path);
+		if (rc && rc == -EREMOTE) {
+			struct smb_vol v = {NULL};
+			/* if @path contains a tree name, skip it in the prefix path */
+			if (added_treename) {
+				rc = cifs_parse_devname(path, &v);
+				if (rc)
+					break;
+				rc = -EREMOTE;
+				npath = build_unc_path_to_root(&v, cifs_sb, true);
+				cifs_cleanup_volume_info_contents(&v);
+			} else {
+				v.UNC = vol->UNC;
+				v.prepath = path + 1;
+				npath = build_unc_path_to_root(&v, cifs_sb, true);
+			}
+			if (IS_ERR(npath)) {
+				rc = PTR_ERR(npath);
+				break;
+			}
+			kfree(*dfs_path);
+			*dfs_path = npath;
+		}
+		*s = tmp;
+	} while (rc == 0);
+
+	kfree(path);
+	return rc;
 }
 
 int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
 {
 	int rc = 0;
 	unsigned int xid;
-	struct cifs_ses *ses;
-	struct cifs_tcon *root_tcon = NULL;
+	struct TCP_Server_Info *server = NULL;
+	struct cifs_ses *ses = NULL, *root_ses = NULL;
 	struct cifs_tcon *tcon = NULL;
-	struct TCP_Server_Info *server;
-	char *root_path = NULL, *full_path = NULL;
-	char *old_mountdata, *origin_mountdata = NULL;
-	int count;
+	int count = 0;
+	char *ref_path = NULL, *full_path = NULL;
+	char *oldmnt = NULL;
+	char *mntdata = NULL;
 
 	rc = mount_get_conns(vol, cifs_sb, &xid, &server, &ses, &tcon);
-	if (!rc && tcon) {
-		/* If not a standalone DFS root, then check if path is remote */
-		rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
-				    cifs_remap(cifs_sb), vol->UNC + 1, NULL,
-				    NULL);
-		if (rc) {
-			rc = is_path_remote(cifs_sb, vol, xid, server, tcon);
-			if (!rc)
-				goto out;
-			if (rc != -EREMOTE)
-				goto error;
-		}
-	}
 	/*
-	 * If first DFS target server went offline and we failed to connect it,
-	 * server and ses pointers are NULL at this point, though we still have
-	 * chance to get a cached DFS referral in expand_dfs_referral() and
-	 * retry next target available in it.
+	 * Unconditionally try to get an DFS referral (even cached) to determine whether it is an
+	 * DFS mount.
 	 *
-	 * If a NULL ses ptr is passed to dfs_cache_find(), a lookup will be
-	 * performed against DFS path and *no* requests will be sent to server
-	 * for any new DFS referrals. Hence it's safe to skip checking whether
-	 * server or ses ptr is NULL.
+	 * Skip prefix path to provide support for DFS referrals from w2k8 servers which don't seem
+	 * to respond with PATH_NOT_COVERED to requests that include the prefix.
 	 */
-	if (rc == -EACCES || rc == -EOPNOTSUPP)
-		goto error;
-
-	root_path = build_unc_path_to_root(vol, cifs_sb, false);
-	if (IS_ERR(root_path)) {
-		rc = PTR_ERR(root_path);
-		root_path = NULL;
-		goto error;
-	}
-
-	full_path = build_unc_path_to_root(vol, cifs_sb, true);
-	if (IS_ERR(full_path)) {
-		rc = PTR_ERR(full_path);
-		full_path = NULL;
-		goto error;
-	}
-	/*
-	 * Perform an unconditional check for whether there are DFS
-	 * referrals for this path without prefix, to provide support
-	 * for DFS referrals from w2k8 servers which don't seem to respond
-	 * with PATH_NOT_COVERED to requests that include the prefix.
-	 * Chase the referral if found, otherwise continue normally.
-	 */
-	old_mountdata = cifs_sb->mountdata;
-	(void)expand_dfs_referral(xid, ses, vol, cifs_sb, false);
-
-	if (cifs_sb->mountdata == NULL) {
-		rc = -ENOENT;
-		goto error;
+	if (dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb), vol->UNC + 1, NULL,
+			   NULL)) {
+		/* No DFS referral was returned.  Looks like a regular share. */
+		if (rc)
+			goto error;
+		/* Check if it is fully accessible and then mount it */
+		rc = is_path_remote(cifs_sb, vol, xid, server, tcon);
+		if (!rc)
+			goto out;
+		if (rc != -EREMOTE)
+			goto error;
 	}
-
-	/* Save DFS root volume information for DFS refresh worker */
-	origin_mountdata = kstrndup(cifs_sb->mountdata,
-				    strlen(cifs_sb->mountdata), GFP_KERNEL);
-	if (!origin_mountdata) {
+	/* Save mount options */
+	mntdata = kstrndup(cifs_sb->mountdata, strlen(cifs_sb->mountdata), GFP_KERNEL);
+	if (!mntdata) {
 		rc = -ENOMEM;
 		goto error;
 	}
-
-	if (cifs_sb->mountdata != old_mountdata) {
-		/* If we were redirected, reconnect to new target server */
-		mount_put_conns(cifs_sb, xid, server, ses, tcon);
-		rc = mount_get_conns(vol, cifs_sb, &xid, &server, &ses, &tcon);
-	}
-	if (rc) {
-		if (rc == -EACCES || rc == -EOPNOTSUPP)
-			goto error;
-		/* Perform DFS failover to any other DFS targets */
-		rc = mount_do_dfs_failover(root_path + 1, cifs_sb, vol, NULL,
-					   &xid, &server, &ses, &tcon);
-		if (rc)
-			goto error;
-	}
-
-	kfree(root_path);
-	root_path = build_unc_path_to_root(vol, cifs_sb, false);
-	if (IS_ERR(root_path)) {
-		rc = PTR_ERR(root_path);
-		root_path = NULL;
+	/* Get path of DFS root */
+	ref_path = build_unc_path_to_root(vol, cifs_sb, false);
+	if (IS_ERR(ref_path)) {
+		rc = PTR_ERR(ref_path);
+		ref_path = NULL;
 		goto error;
 	}
-	/* Cache out resolved root server */
-	(void)dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
-			     root_path + 1, NULL, NULL);
-	kfree(root_path);
-	root_path = NULL;
-
-	set_root_tcon(cifs_sb, tcon, &root_tcon);
-
-	for (count = 1; ;) {
-		if (!rc && tcon) {
-			rc = is_path_remote(cifs_sb, vol, xid, server, tcon);
-			if (!rc || rc != -EREMOTE)
-				break;
-		}
-		/*
-		 * BB: when we implement proper loop detection,
-		 *     we will remove this check. But now we need it
-		 *     to prevent an indefinite loop if 'DFS tree' is
-		 *     misconfigured (i.e. has loops).
-		 */
-		if (count++ > MAX_NESTED_LINKS) {
-			rc = -ELOOP;
-			break;
-		}
 
+	set_root_ses(cifs_sb, ses, &root_ses);
+	do {
+		/* Save full path of last DFS path we used to resolve final target server */
 		kfree(full_path);
-		full_path = build_unc_path_to_root(vol, cifs_sb, true);
+		full_path = build_unc_path_to_root(vol, cifs_sb, !!count);
 		if (IS_ERR(full_path)) {
 			rc = PTR_ERR(full_path);
-			full_path = NULL;
 			break;
 		}
-
-		old_mountdata = cifs_sb->mountdata;
-		rc = expand_dfs_referral(xid, root_tcon->ses, vol, cifs_sb,
-					 true);
+		/* Chase referral */
+		oldmnt = cifs_sb->mountdata;
+		rc = expand_dfs_referral(xid, root_ses, vol, cifs_sb, ref_path + 1);
 		if (rc)
 			break;
-
-		if (cifs_sb->mountdata != old_mountdata) {
+		/* Connect to new DFS target only if we were redirected */
+		if (oldmnt != cifs_sb->mountdata) {
 			mount_put_conns(cifs_sb, xid, server, ses, tcon);
-			rc = mount_get_conns(vol, cifs_sb, &xid, &server, &ses,
-					     &tcon);
-			/*
-			 * Ensure that DFS referrals go through new root server.
-			 */
-			if (!rc && tcon &&
-			    (tcon->share_flags & (SHI1005_FLAGS_DFS |
-						  SHI1005_FLAGS_DFS_ROOT))) {
-				cifs_put_tcon(root_tcon);
-				set_root_tcon(cifs_sb, tcon, &root_tcon);
-			}
+			rc = mount_get_conns(vol, cifs_sb, &xid, &server, &ses, &tcon);
 		}
-		if (rc) {
-			if (rc == -EACCES || rc == -EOPNOTSUPP)
-				break;
-			/* Perform DFS failover to any other DFS targets */
-			rc = mount_do_dfs_failover(full_path + 1, cifs_sb, vol,
-						   root_tcon->ses, &xid,
-						   &server, &ses, &tcon);
-			if (rc == -EACCES || rc == -EOPNOTSUPP || !server ||
-			    !ses)
-				goto error;
+		if (rc && !server && !ses) {
+			/* Failed to connect. Try to connect to other targets in the referral. */
+			rc = do_dfs_failover(ref_path + 1, full_path, cifs_sb, vol, root_ses, &xid,
+					     &server, &ses, &tcon);
 		}
-	}
-	cifs_put_tcon(root_tcon);
+		if (rc == -EACCES || rc == -EOPNOTSUPP || !server || !ses)
+			break;
+		if (!tcon)
+			continue;
+		/* Make sure that requests go through new root servers */
+		if (tcon->share_flags & (SHI1005_FLAGS_DFS | SHI1005_FLAGS_DFS_ROOT)) {
+			put_root_ses(root_ses);
+			set_root_ses(cifs_sb, ses, &root_ses);
+		}
+		/* Check for remaining path components and then continue chasing them (-EREMOTE) */
+		rc = check_dfs_prepath(cifs_sb, vol, xid, server, tcon, &ref_path);
+		/* Prevent recursion on broken link referrals */
+		if (rc == -EREMOTE && ++count > MAX_NESTED_LINKS)
+			rc = -ELOOP;
+	} while (rc == -EREMOTE);
 
 	if (rc)
 		goto error;
-
-	spin_lock(&cifs_tcp_ses_lock);
-	if (!tcon->dfs_path) {
-		/* Save full path in new tcon to do failover when reconnecting tcons */
-		tcon->dfs_path = full_path;
-		full_path = NULL;
-		tcon->remap = cifs_remap(cifs_sb);
-	}
-	cifs_sb->origin_fullpath = kstrndup(tcon->dfs_path,
-					    strlen(tcon->dfs_path),
-					    GFP_ATOMIC);
+	put_root_ses(root_ses);
+	root_ses = NULL;
+	kfree(ref_path);
+	ref_path = NULL;
+	/*
+	 * Store DFS full path in both superblock and tree connect structures.
+	 *
+	 * For DFS root mounts, the prefix path (cifs_sb->prepath) is preserved during reconnect so
+	 * only the root path is set in cifs_sb->origin_fullpath and tcon->dfs_path. And for DFS
+	 * links, the prefix path is included in both and may be changed during reconnect.  See
+	 * cifs_tree_connect().
+	 */
+	cifs_sb->origin_fullpath = kstrndup(full_path, strlen(full_path), GFP_KERNEL);
 	if (!cifs_sb->origin_fullpath) {
-		spin_unlock(&cifs_tcp_ses_lock);
 		rc = -ENOMEM;
 		goto error;
 	}
+	spin_lock(&cifs_tcp_ses_lock);
+	tcon->dfs_path = full_path;
+	full_path = NULL;
+	tcon->remap = cifs_remap(cifs_sb);
 	spin_unlock(&cifs_tcp_ses_lock);
 
-	rc = dfs_cache_add_vol(origin_mountdata, vol, cifs_sb->origin_fullpath);
-	if (rc) {
-		kfree(cifs_sb->origin_fullpath);
+	/* Add original volume information for DFS cache to be used when refreshing referrals */
+	rc = dfs_cache_add_vol(mntdata, vol, cifs_sb->origin_fullpath);
+	if (rc)
 		goto error;
-	}
 	/*
 	 * After reconnecting to a different server, unique ids won't
 	 * match anymore, so we disable serverino. This prevents
@@ -4976,9 +4969,11 @@ out:
 	return mount_setup_tlink(cifs_sb, ses, tcon);
 
 error:
+	kfree(ref_path);
 	kfree(full_path);
-	kfree(root_path);
-	kfree(origin_mountdata);
+	kfree(mntdata);
+	kfree(cifs_sb->origin_fullpath);
+	put_root_ses(root_ses);
 	mount_put_conns(cifs_sb, xid, server, ses, tcon);
 	return rc;
 }
@@ -5114,8 +5109,7 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 	bcc_ptr += strlen("?????");
 	bcc_ptr += 1;
 	count = bcc_ptr - &pSMB->Password[0];
-	pSMB->hdr.smb_buf_length = cpu_to_be32(be32_to_cpu(
-					pSMB->hdr.smb_buf_length) + count);
+	be32_add_cpu(&pSMB->hdr.smb_buf_length, count);
 	pSMB->ByteCount = cpu_to_le16(count);
 
 	rc = SendReceive(xid, ses, smb_buffer, smb_buffer_response, &length,
@@ -5533,3 +5527,115 @@ cifs_prune_tlinks(struct work_struct *work)
 	queue_delayed_work(cifsiod_wq, &cifs_sb->prune_tlinks,
 				TLINK_IDLE_EXPIRE);
 }
+
+#ifdef CONFIG_CIFS_DFS_UPCALL
+int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
+{
+	int rc;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	const struct smb_version_operations *ops = server->ops;
+	struct dfs_cache_tgt_list tl;
+	struct dfs_cache_tgt_iterator *it = NULL;
+	char *tree;
+	const char *tcp_host;
+	size_t tcp_host_len;
+	const char *dfs_host;
+	size_t dfs_host_len;
+	char *share = NULL, *prefix = NULL;
+	struct dfs_info3_param ref = {0};
+	bool isroot;
+
+	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
+	if (!tree)
+		return -ENOMEM;
+
+	if (!tcon->dfs_path) {
+		if (tcon->ipc) {
+			scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
+		} else {
+			rc = ops->tree_connect(xid, tcon->ses, tcon->treeName, tcon, nlsc);
+		}
+		goto out;
+	}
+
+	rc = dfs_cache_noreq_find(tcon->dfs_path + 1, &ref, &tl);
+	if (rc)
+		goto out;
+	isroot = ref.server_type == DFS_TYPE_ROOT;
+	free_dfs_info_param(&ref);
+
+	extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
+
+	for (it = dfs_cache_get_tgt_iterator(&tl); it; it = dfs_cache_get_next_tgt(&tl, it)) {
+		bool target_match;
+
+		kfree(share);
+		kfree(prefix);
+		share = NULL;
+		prefix = NULL;
+
+		rc = dfs_cache_get_tgt_share(tcon->dfs_path + 1, it, &share, &prefix);
+		if (rc) {
+			cifs_dbg(VFS, "%s: failed to parse target share %d\n",
+				 __func__, rc);
+			continue;
+		}
+
+		extract_unc_hostname(share, &dfs_host, &dfs_host_len);
+
+		if (dfs_host_len != tcp_host_len
+		    || strncasecmp(dfs_host, tcp_host, dfs_host_len) != 0) {
+			cifs_dbg(FYI, "%s: %.*s doesn't match %.*s\n", __func__, (int)dfs_host_len,
+				 dfs_host, (int)tcp_host_len, tcp_host);
+
+			rc = match_target_ip(server, dfs_host, dfs_host_len, &target_match);
+			if (rc) {
+				cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
+				break;
+			}
+
+			if (!target_match) {
+				cifs_dbg(FYI, "%s: skipping target\n", __func__);
+				continue;
+			}
+		}
+
+		if (tcon->ipc) {
+			scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", share);
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
+		} else {
+			scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
+			/* Only handle prefix paths of DFS link targets */
+			if (!rc && !isroot) {
+				rc = update_super_prepath(tcon, prefix);
+				break;
+			}
+		}
+		if (rc == -EREMOTE)
+			break;
+	}
+
+	kfree(share);
+	kfree(prefix);
+
+	if (!rc) {
+		if (it)
+			rc = dfs_cache_noreq_update_tgthint(tcon->dfs_path + 1, it);
+		else
+			rc = -ENOENT;
+	}
+	dfs_cache_free_tgts(&tl);
+out:
+	kfree(tree);
+	return rc;
+}
+#else
+int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
+{
+	const struct smb_version_operations *ops = tcon->ses->server->ops;
+
+	return ops->tree_connect(xid, tcon->ses, tcon->treeName, tcon, nlsc);
+}
+#endif