1 files changed, 544 insertions, 0 deletions

diff --git a/fs/cifs/dfs.c b/fs/cifs/dfs.c
new file mode 100644
index 000000000000..b541e68378f6
--- /dev/null
+++ b/fs/cifs/dfs.c
@@ -0,0 +1,544 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Paulo Alcantara <palcantara@suse.de>
+ */
+
+#include <linux/namei.h>
+#include "cifsproto.h"
+#include "cifs_debug.h"
+#include "dns_resolve.h"
+#include "fs_context.h"
+#include "dfs.h"
+
+/**
+ * dfs_parse_target_referral - set fs context for dfs target referral
+ *
+ * @full_path: full path in UNC format.
+ * @ref: dfs referral pointer.
+ * @ctx: smb3 fs context pointer.
+ *
+ * Return zero if dfs referral was parsed correctly, otherwise non-zero.
+ */
+int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
+			      struct smb3_fs_context *ctx)
+{
+	int rc;
+	const char *prepath = NULL;
+	char *path;
+
+	if (!full_path || !*full_path || !ref || !ctx)
+		return -EINVAL;
+
+	if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
+		return -EINVAL;
+
+	if (strlen(full_path) - ref->path_consumed) {
+		prepath = full_path + ref->path_consumed;
+		/* skip initial delimiter */
+		if (*prepath == '/' || *prepath == '\\')
+			prepath++;
+	}
+
+	path = cifs_build_devname(ref->node_name, prepath);
+	if (IS_ERR(path))
+		return PTR_ERR(path);
+
+	rc = smb3_parse_devname(path, ctx);
+	if (rc)
+		goto out;
+
+	rc = dns_resolve_server_name_to_ip(path, (struct sockaddr *)&ctx->dstaddr, NULL);
+
+out:
+	kfree(path);
+	return rc;
+}
+
+/*
+ * cifs_build_path_to_root returns full path to root when we do not have an
+ * existing connection (tcon)
+ */
+static char *build_unc_path_to_root(const struct smb3_fs_context *ctx,
+				    const struct cifs_sb_info *cifs_sb, bool useppath)
+{
+	char *full_path, *pos;
+	unsigned int pplen = useppath && ctx->prepath ? strlen(ctx->prepath) + 1 : 0;
+	unsigned int unc_len = strnlen(ctx->UNC, MAX_TREE_SIZE + 1);
+
+	if (unc_len > MAX_TREE_SIZE)
+		return ERR_PTR(-EINVAL);
+
+	full_path = kmalloc(unc_len + pplen + 1, GFP_KERNEL);
+	if (full_path == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	memcpy(full_path, ctx->UNC, unc_len);
+	pos = full_path + unc_len;
+
+	if (pplen) {
+		*pos = CIFS_DIR_SEP(cifs_sb);
+		memcpy(pos + 1, ctx->prepath, pplen);
+		pos += pplen;
+	}
+
+	*pos = '\0'; /* add trailing null */
+	convert_delimiter(full_path, CIFS_DIR_SEP(cifs_sb));
+	cifs_dbg(FYI, "%s: full_path=%s\n", __func__, full_path);
+	return full_path;
+}
+
+static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
+{
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	int rc;
+
+	ctx->leaf_fullpath = (char *)full_path;
+	rc = cifs_mount_get_session(mnt_ctx);
+	ctx->leaf_fullpath = NULL;
+	if (!rc) {
+		struct cifs_ses *ses = mnt_ctx->ses;
+
+		mutex_lock(&ses->session_mutex);
+		ses->dfs_root_ses = mnt_ctx->root_ses;
+		mutex_unlock(&ses->session_mutex);
+	}
+	return rc;
+}
+
+static void set_root_ses(struct cifs_mount_ctx *mnt_ctx)
+{
+	if (mnt_ctx->ses) {
+		spin_lock(&cifs_tcp_ses_lock);
+		mnt_ctx->ses->ses_count++;
+		spin_unlock(&cifs_tcp_ses_lock);
+		dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, mnt_ctx->ses);
+	}
+	mnt_ctx->root_ses = mnt_ctx->ses;
+}
+
+static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, const char *full_path,
+			const struct dfs_cache_tgt_iterator *tit)
+{
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	struct dfs_info3_param ref = {};
+	int rc;
+
+	rc = dfs_cache_get_tgt_referral(ref_path + 1, tit, &ref);
+	if (rc)
+		return rc;
+
+	rc = dfs_parse_target_referral(full_path + 1, &ref, ctx);
+	if (rc)
+		goto out;
+
+	cifs_mount_put_conns(mnt_ctx);
+	rc = get_session(mnt_ctx, ref_path);
+	if (rc)
+		goto out;
+
+	if (ref.flags & DFSREF_REFERRAL_SERVER)
+		set_root_ses(mnt_ctx);
+
+	rc = -EREMOTE;
+	if (ref.flags & DFSREF_STORAGE_SERVER) {
+		rc = cifs_mount_get_tcon(mnt_ctx);
+		if (rc)
+			goto out;
+
+		/* some servers may not advertise referral capability under ref.flags */
+		if (!(ref.flags & DFSREF_REFERRAL_SERVER) &&
+		    is_tcon_dfs(mnt_ctx->tcon))
+			set_root_ses(mnt_ctx);
+
+		rc = cifs_is_path_remote(mnt_ctx);
+	}
+
+out:
+	free_dfs_info_param(&ref);
+	return rc;
+}
+
+static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
+{
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	char *ref_path = NULL, *full_path = NULL;
+	struct dfs_cache_tgt_iterator *tit;
+	struct TCP_Server_Info *server;
+	char *origin_fullpath = NULL;
+	int num_links = 0;
+	int rc;
+
+	ref_path = dfs_get_path(cifs_sb, ctx->UNC);
+	if (IS_ERR(ref_path))
+		return PTR_ERR(ref_path);
+
+	full_path = build_unc_path_to_root(ctx, cifs_sb, true);
+	if (IS_ERR(full_path)) {
+		rc = PTR_ERR(full_path);
+		full_path = NULL;
+		goto out;
+	}
+
+	origin_fullpath = kstrdup(full_path, GFP_KERNEL);
+	if (!origin_fullpath) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	do {
+		struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
+
+		rc = dfs_get_referral(mnt_ctx, ref_path + 1, NULL, &tl);
+		if (rc)
+			break;
+
+		tit = dfs_cache_get_tgt_iterator(&tl);
+		if (!tit) {
+			cifs_dbg(VFS, "%s: dfs referral (%s) with no targets\n", __func__,
+				 ref_path + 1);
+			rc = -ENOENT;
+			dfs_cache_free_tgts(&tl);
+			break;
+		}
+
+		do {
+			rc = get_dfs_conn(mnt_ctx, ref_path, full_path, tit);
+			if (!rc)
+				break;
+			if (rc == -EREMOTE) {
+				if (++num_links > MAX_NESTED_LINKS) {
+					rc = -ELOOP;
+					break;
+				}
+				kfree(ref_path);
+				kfree(full_path);
+				ref_path = full_path = NULL;
+
+				full_path = build_unc_path_to_root(ctx, cifs_sb, true);
+				if (IS_ERR(full_path)) {
+					rc = PTR_ERR(full_path);
+					full_path = NULL;
+				} else {
+					ref_path = dfs_get_path(cifs_sb, full_path);
+					if (IS_ERR(ref_path)) {
+						rc = PTR_ERR(ref_path);
+						ref_path = NULL;
+					}
+				}
+				break;
+			}
+		} while ((tit = dfs_cache_get_next_tgt(&tl, tit)));
+		dfs_cache_free_tgts(&tl);
+	} while (rc == -EREMOTE);
+
+	if (!rc) {
+		server = mnt_ctx->server;
+
+		mutex_lock(&server->refpath_lock);
+		server->origin_fullpath = origin_fullpath;
+		server->current_fullpath = server->leaf_fullpath;
+		mutex_unlock(&server->refpath_lock);
+		origin_fullpath = NULL;
+	}
+
+out:
+	kfree(origin_fullpath);
+	kfree(ref_path);
+	kfree(full_path);
+	return rc;
+}
+
+int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
+{
+	struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	int rc;
+
+	*isdfs = false;
+
+	rc = get_session(mnt_ctx, NULL);
+	if (rc)
+		return rc;
+	mnt_ctx->root_ses = mnt_ctx->ses;
+	/*
+	 * If called with 'nodfs' mount option, then skip DFS resolving.  Otherwise unconditionally
+	 * try to get an DFS referral (even cached) to determine whether it is an DFS mount.
+	 *
+	 * 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 ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) ||
+	    dfs_get_referral(mnt_ctx, ctx->UNC + 1, NULL, NULL)) {
+		rc = cifs_mount_get_tcon(mnt_ctx);
+		if (rc)
+			return rc;
+
+		rc = cifs_is_path_remote(mnt_ctx);
+		if (!rc || rc != -EREMOTE)
+			return rc;
+	}
+
+	*isdfs = true;
+	set_root_ses(mnt_ctx);
+
+	return __dfs_mount_share(mnt_ctx);
+}
+
+/* Update dfs referral path of superblock */
+static int update_server_fullpath(struct TCP_Server_Info *server, struct cifs_sb_info *cifs_sb,
+				  const char *target)
+{
+	int rc = 0;
+	size_t len = strlen(target);
+	char *refpath, *npath;
+
+	if (unlikely(len < 2 || *target != '\\'))
+		return -EINVAL;
+
+	if (target[1] == '\\') {
+		len += 1;
+		refpath = kmalloc(len, GFP_KERNEL);
+		if (!refpath)
+			return -ENOMEM;
+
+		scnprintf(refpath, len, "%s", target);
+	} else {
+		len += sizeof("\\");
+		refpath = kmalloc(len, GFP_KERNEL);
+		if (!refpath)
+			return -ENOMEM;
+
+		scnprintf(refpath, len, "\\%s", target);
+	}
+
+	npath = dfs_cache_canonical_path(refpath, cifs_sb->local_nls, cifs_remap(cifs_sb));
+	kfree(refpath);
+
+	if (IS_ERR(npath)) {
+		rc = PTR_ERR(npath);
+	} else {
+		mutex_lock(&server->refpath_lock);
+		kfree(server->leaf_fullpath);
+		server->leaf_fullpath = npath;
+		mutex_unlock(&server->refpath_lock);
+		server->current_fullpath = server->leaf_fullpath;
+	}
+	return rc;
+}
+
+static int target_share_matches_server(struct TCP_Server_Info *server, const char *tcp_host,
+				       size_t tcp_host_len, char *share, bool *target_match)
+{
+	int rc = 0;
+	const char *dfs_host;
+	size_t dfs_host_len;
+
+	*target_match = true;
+	extract_unc_hostname(share, &dfs_host, &dfs_host_len);
+
+	/* Check if hostnames or addresses match */
+	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);
+	}
+	return rc;
+}
+
+static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
+				     struct cifs_sb_info *cifs_sb, char *tree, bool islink,
+				     struct dfs_cache_tgt_list *tl)
+{
+	int rc;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	const struct smb_version_operations *ops = server->ops;
+	struct cifs_ses *root_ses = CIFS_DFS_ROOT_SES(tcon->ses);
+	struct cifs_tcon *ipc = root_ses->tcon_ipc;
+	char *share = NULL, *prefix = NULL;
+	const char *tcp_host;
+	size_t tcp_host_len;
+	struct dfs_cache_tgt_iterator *tit;
+	bool target_match;
+
+	extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
+
+	tit = dfs_cache_get_tgt_iterator(tl);
+	if (!tit) {
+		rc = -ENOENT;
+		goto out;
+	}
+
+	/* Try to tree connect to all dfs targets */
+	for (; tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
+		const char *target = dfs_cache_get_tgt_name(tit);
+		struct dfs_cache_tgt_list ntl = DFS_CACHE_TGT_LIST_INIT(ntl);
+
+		kfree(share);
+		kfree(prefix);
+		share = prefix = NULL;
+
+		/* Check if share matches with tcp ses */
+		rc = dfs_cache_get_tgt_share(server->current_fullpath + 1, tit, &share, &prefix);
+		if (rc) {
+			cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
+			break;
+		}
+
+		rc = target_share_matches_server(server, tcp_host, tcp_host_len, share,
+						 &target_match);
+		if (rc)
+			break;
+		if (!target_match) {
+			rc = -EHOSTUNREACH;
+			continue;
+		}
+
+		dfs_cache_noreq_update_tgthint(server->current_fullpath + 1, tit);
+
+		if (ipc->need_reconnect) {
+			scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
+			rc = ops->tree_connect(xid, ipc->ses, tree, ipc, cifs_sb->local_nls);
+			if (rc)
+				break;
+		}
+
+		scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
+		if (!islink) {
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
+			break;
+		}
+		/*
+		 * If no dfs referrals were returned from link target, then just do a TREE_CONNECT
+		 * to it.  Otherwise, cache the dfs referral and then mark current tcp ses for
+		 * reconnect so either the demultiplex thread or the echo worker will reconnect to
+		 * newly resolved target.
+		 */
+		if (dfs_cache_find(xid, root_ses, cifs_sb->local_nls, cifs_remap(cifs_sb), target,
+				   NULL, &ntl)) {
+			rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
+			if (rc)
+				continue;
+
+			rc = cifs_update_super_prepath(cifs_sb, prefix);
+		} else {
+			/* Target is another dfs share */
+			rc = update_server_fullpath(server, cifs_sb, target);
+			dfs_cache_free_tgts(tl);
+
+			if (!rc) {
+				rc = -EREMOTE;
+				list_replace_init(&ntl.tl_list, &tl->tl_list);
+			} else
+				dfs_cache_free_tgts(&ntl);
+		}
+		break;
+	}
+
+out:
+	kfree(share);
+	kfree(prefix);
+
+	return rc;
+}
+
+static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
+				   struct cifs_sb_info *cifs_sb, char *tree, bool islink,
+				   struct dfs_cache_tgt_list *tl)
+{
+	int rc;
+	int num_links = 0;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	char *old_fullpath = server->leaf_fullpath;
+
+	do {
+		rc = __tree_connect_dfs_target(xid, tcon, cifs_sb, tree, islink, tl);
+		if (!rc || rc != -EREMOTE)
+			break;
+	} while (rc = -ELOOP, ++num_links < MAX_NESTED_LINKS);
+	/*
+	 * If we couldn't tree connect to any targets from last referral path, then
+	 * retry it from newly resolved dfs referral.
+	 */
+	if (rc && server->leaf_fullpath != old_fullpath)
+		cifs_signal_cifsd_for_reconnect(server, true);
+
+	dfs_cache_free_tgts(tl);
+	return rc;
+}
+
+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 super_block *sb = NULL;
+	struct cifs_sb_info *cifs_sb;
+	struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
+	char *tree;
+	struct dfs_info3_param ref = {0};
+
+	/* only send once per connect */
+	spin_lock(&tcon->tc_lock);
+	if (tcon->ses->ses_status != SES_GOOD ||
+	    (tcon->status != TID_NEW &&
+	    tcon->status != TID_NEED_TCON)) {
+		spin_unlock(&tcon->tc_lock);
+		return 0;
+	}
+	tcon->status = TID_IN_TCON;
+	spin_unlock(&tcon->tc_lock);
+
+	tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
+	if (!tree) {
+		rc = -ENOMEM;
+		goto out;
+	}
+
+	if (tcon->ipc) {
+		scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
+		rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
+		goto out;
+	}
+
+	sb = cifs_get_tcp_super(server);
+	if (IS_ERR(sb)) {
+		rc = PTR_ERR(sb);
+		cifs_dbg(VFS, "%s: could not find superblock: %d\n", __func__, rc);
+		goto out;
+	}
+
+	cifs_sb = CIFS_SB(sb);
+
+	/* If it is not dfs or there was no cached dfs referral, then reconnect to same share */
+	if (!server->current_fullpath ||
+	    dfs_cache_noreq_find(server->current_fullpath + 1, &ref, &tl)) {
+		rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name, tcon, cifs_sb->local_nls);
+		goto out;
+	}
+
+	rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
+				     &tl);
+	free_dfs_info_param(&ref);
+
+out:
+	kfree(tree);
+	cifs_put_tcp_super(sb);
+
+	if (rc) {
+		spin_lock(&tcon->tc_lock);
+		if (tcon->status == TID_IN_TCON)
+			tcon->status = TID_NEED_TCON;
+		spin_unlock(&tcon->tc_lock);
+	} else {
+		spin_lock(&tcon->tc_lock);
+		if (tcon->status == TID_IN_TCON)
+			tcon->status = TID_GOOD;
+		spin_unlock(&tcon->tc_lock);
+		tcon->need_reconnect = false;
+	}
+
+	return rc;
+}