1 files changed, 467 insertions, 0 deletions

diff --git a/fs/smb/client/dfs.c b/fs/smb/client/dfs.c
new file mode 100644
index 000000000000..f65a8a90ba27
--- /dev/null
+++ b/fs/smb/client/dfs.c
@@ -0,0 +1,467 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Paulo Alcantara <palcantara@suse.de>
+ */
+
+#include "cifsproto.h"
+#include "cifs_debug.h"
+#include "dns_resolve.h"
+#include "fs_context.h"
+#include "dfs.h"
+
+#define DFS_DOM(ctx) (ctx->dfs_root_ses ? ctx->dfs_root_ses->dns_dom : NULL)
+
+/**
+ * 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_unc(DFS_DOM(ctx), path,
+			     (struct sockaddr *)&ctx->dstaddr);
+out:
+	kfree(path);
+	return rc;
+}
+
+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;
+	ctx->dns_dom = DFS_DOM(ctx);
+	rc = cifs_mount_get_session(mnt_ctx);
+	ctx->leaf_fullpath = ctx->dns_dom = NULL;
+
+	return rc;
+}
+
+/*
+ * Get an active reference of @ses so that next call to cifs_put_tcon() won't
+ * release it as any new DFS referrals must go through its IPC tcon.
+ */
+static void set_root_smb_session(struct cifs_mount_ctx *mnt_ctx)
+{
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	struct cifs_ses *ses = mnt_ctx->ses;
+
+	if (ses) {
+		spin_lock(&cifs_tcp_ses_lock);
+		cifs_smb_ses_inc_refcount(ses);
+		spin_unlock(&cifs_tcp_ses_lock);
+	}
+	ctx->dfs_root_ses = ses;
+}
+
+static inline int parse_dfs_target(struct smb3_fs_context *ctx,
+				   struct dfs_ref_walk *rw,
+				   struct dfs_info3_param *tgt)
+{
+	int rc;
+	const char *fpath = ref_walk_fpath(rw) + 1;
+
+	rc = ref_walk_get_tgt(rw, tgt);
+	if (!rc)
+		rc = dfs_parse_target_referral(fpath, tgt, ctx);
+	return rc;
+}
+
+static int setup_dfs_ref(struct dfs_info3_param *tgt, struct dfs_ref_walk *rw)
+{
+	struct cifs_sb_info *cifs_sb = rw->mnt_ctx->cifs_sb;
+	struct smb3_fs_context *ctx = rw->mnt_ctx->fs_ctx;
+	char *ref_path, *full_path;
+	int rc;
+
+	set_root_smb_session(rw->mnt_ctx);
+	ref_walk_ses(rw) = ctx->dfs_root_ses;
+
+	full_path = smb3_fs_context_fullpath(ctx, CIFS_DIR_SEP(cifs_sb));
+	if (IS_ERR(full_path))
+		return PTR_ERR(full_path);
+
+	if (!tgt || (tgt->server_type == DFS_TYPE_LINK &&
+		     DFS_INTERLINK(tgt->flags)))
+		ref_path = dfs_get_path(cifs_sb, ctx->UNC);
+	else
+		ref_path = dfs_get_path(cifs_sb, full_path);
+	if (IS_ERR(ref_path)) {
+		rc = PTR_ERR(ref_path);
+		kfree(full_path);
+		return rc;
+	}
+	ref_walk_path(rw) = ref_path;
+	ref_walk_fpath(rw) = full_path;
+
+	return dfs_get_referral(rw->mnt_ctx,
+				ref_walk_path(rw) + 1,
+				ref_walk_tl(rw));
+}
+
+static int __dfs_referral_walk(struct dfs_ref_walk *rw)
+{
+	struct smb3_fs_context *ctx = rw->mnt_ctx->fs_ctx;
+	struct cifs_mount_ctx *mnt_ctx = rw->mnt_ctx;
+	struct dfs_info3_param tgt = {};
+	int rc = -ENOENT;
+
+again:
+	do {
+		ctx->dfs_root_ses = ref_walk_ses(rw);
+		while (ref_walk_next_tgt(rw)) {
+			rc = parse_dfs_target(ctx, rw, &tgt);
+			if (rc)
+				continue;
+
+			cifs_mount_put_conns(mnt_ctx);
+			rc = get_session(mnt_ctx, ref_walk_path(rw));
+			if (rc)
+				continue;
+
+			rc = cifs_mount_get_tcon(mnt_ctx);
+			if (rc) {
+				if (tgt.server_type == DFS_TYPE_LINK &&
+				    DFS_INTERLINK(tgt.flags))
+					rc = -EREMOTE;
+			} else {
+				rc = cifs_is_path_remote(mnt_ctx);
+				if (!rc) {
+					ref_walk_set_tgt_hint(rw);
+					break;
+				}
+			}
+			if (rc == -EREMOTE) {
+				rc = ref_walk_advance(rw);
+				if (!rc) {
+					rc = setup_dfs_ref(&tgt, rw);
+					if (rc)
+						break;
+					ref_walk_mark_end(rw);
+					goto again;
+				}
+			}
+		}
+	} while (rc && ref_walk_descend(rw));
+
+	free_dfs_info_param(&tgt);
+	return rc;
+}
+
+static int dfs_referral_walk(struct cifs_mount_ctx *mnt_ctx,
+			     struct dfs_ref_walk **rw)
+{
+	int rc;
+
+	*rw = ref_walk_alloc();
+	if (IS_ERR(*rw)) {
+		rc = PTR_ERR(*rw);
+		*rw = NULL;
+		return rc;
+	}
+
+	ref_walk_init(*rw, mnt_ctx);
+	rc = setup_dfs_ref(NULL, *rw);
+	if (!rc)
+		rc = __dfs_referral_walk(*rw);
+	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;
+	struct dfs_ref_walk *rw = NULL;
+	struct cifs_tcon *tcon;
+	char *origin_fullpath;
+	int rc;
+
+	origin_fullpath = dfs_get_path(cifs_sb, ctx->source);
+	if (IS_ERR(origin_fullpath))
+		return PTR_ERR(origin_fullpath);
+
+	rc = dfs_referral_walk(mnt_ctx, &rw);
+	if (!rc) {
+		/*
+		 * Prevent superblock from being created with any missing
+		 * connections.
+		 */
+		if (WARN_ON(!mnt_ctx->server))
+			rc = -EHOSTDOWN;
+		else if (WARN_ON(!mnt_ctx->ses))
+			rc = -EACCES;
+		else if (WARN_ON(!mnt_ctx->tcon))
+			rc = -ENOENT;
+	}
+	if (rc)
+		goto out;
+
+	tcon = mnt_ctx->tcon;
+	spin_lock(&tcon->tc_lock);
+	tcon->origin_fullpath = origin_fullpath;
+	origin_fullpath = NULL;
+	ref_walk_set_tcon(rw, tcon);
+	spin_unlock(&tcon->tc_lock);
+	queue_delayed_work(dfscache_wq, &tcon->dfs_cache_work,
+			   dfs_cache_get_ttl() * HZ);
+
+out:
+	kfree(origin_fullpath);
+	ref_walk_free(rw);
+	return rc;
+}
+
+/*
+ * If @ctx->dfs_automount, then update @ctx->dstaddr earlier with the DFS root
+ * server from where we'll start following any referrals.  Otherwise rely on the
+ * value provided by mount(2) as the user might not have dns_resolver key set up
+ * and therefore failing to upcall to resolve UNC hostname under @ctx->source.
+ */
+static int update_fs_context_dstaddr(struct smb3_fs_context *ctx)
+{
+	struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
+	int rc = 0;
+
+	if (!ctx->nodfs && ctx->dfs_automount) {
+		rc = dns_resolve_unc(NULL, ctx->source, addr);
+		if (!rc)
+			cifs_set_port(addr, ctx->port);
+		ctx->dfs_automount = false;
+	}
+	return rc;
+}
+
+int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
+{
+	struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+	bool nodfs = ctx->nodfs;
+	int rc;
+
+	rc = update_fs_context_dstaddr(ctx);
+	if (rc)
+		return rc;
+
+	rc = get_session(mnt_ctx, NULL);
+	if (rc)
+		return rc;
+
+	/*
+	 * 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 (!nodfs) {
+		rc = dfs_get_referral(mnt_ctx, ctx->UNC + 1, NULL);
+		if (rc) {
+			cifs_dbg(FYI, "%s: no dfs referral for %s: %d\n",
+				 __func__, ctx->UNC + 1, rc);
+			cifs_dbg(FYI, "%s: assuming non-dfs mount...\n", __func__);
+			nodfs = true;
+		}
+	}
+	if (nodfs) {
+		rc = cifs_mount_get_tcon(mnt_ctx);
+		if (!rc)
+			rc = cifs_is_path_remote(mnt_ctx);
+		return rc;
+	}
+
+	if (!ctx->dfs_conn) {
+		ctx->dfs_conn = true;
+		cifs_mount_put_conns(mnt_ctx);
+		rc = get_session(mnt_ctx, NULL);
+	}
+	if (!rc)
+		rc = __dfs_mount_share(mnt_ctx);
+	return rc;
+}
+
+static int target_share_matches_server(struct TCP_Server_Info *server, 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 */
+	cifs_server_lock(server);
+	if (dfs_host_len != strlen(server->hostname) ||
+	    strncasecmp(dfs_host, server->hostname, dfs_host_len)) {
+		cifs_dbg(FYI, "%s: %.*s doesn't match %s\n", __func__,
+			 (int)dfs_host_len, dfs_host, server->hostname);
+		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);
+	}
+	cifs_server_unlock(server);
+	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)
+{
+	const struct smb_version_operations *ops = tcon->ses->server->ops;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	struct dfs_cache_tgt_iterator *tit;
+	char *share = NULL, *prefix = NULL;
+	bool target_match;
+	int rc = -ENOENT;
+
+	/* Try to tree connect to all dfs targets */
+	for (tit = dfs_cache_get_tgt_iterator(tl);
+	     tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
+		kfree(share);
+		kfree(prefix);
+		share = prefix = NULL;
+
+		/* Check if share matches with tcp ses */
+		rc = dfs_cache_get_tgt_share(server->leaf_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, share, &target_match);
+		if (rc)
+			break;
+		if (!target_match) {
+			rc = -EHOSTUNREACH;
+			continue;
+		}
+
+		dfs_cache_noreq_update_tgthint(server->leaf_fullpath + 1, tit);
+		scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
+		rc = ops->tree_connect(xid, tcon->ses, tree,
+				       tcon, tcon->ses->local_nls);
+		if (islink && !rc && cifs_sb)
+			rc = cifs_update_super_prepath(cifs_sb, prefix);
+		break;
+	}
+
+	kfree(share);
+	kfree(prefix);
+	dfs_cache_free_tgts(tl);
+	return rc;
+}
+
+int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon)
+{
+	int rc;
+	struct TCP_Server_Info *server = tcon->ses->server;
+	const struct smb_version_operations *ops = server->ops;
+	DFS_CACHE_TGT_LIST(tl);
+	struct cifs_sb_info *cifs_sb = NULL;
+	struct super_block *sb = NULL;
+	struct dfs_info3_param ref = {0};
+	char *tree;
+
+	/* only send once per connect */
+	spin_lock(&tcon->tc_lock);
+
+	/* if tcon is marked for needing reconnect, update state */
+	if (tcon->need_reconnect)
+		tcon->status = TID_NEED_TCON;
+
+	if (tcon->status == TID_GOOD) {
+		spin_unlock(&tcon->tc_lock);
+		return 0;
+	}
+
+	if (tcon->status != TID_NEW &&
+	    tcon->status != TID_NEED_TCON) {
+		spin_unlock(&tcon->tc_lock);
+		return -EHOSTDOWN;
+	}
+
+	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) {
+		cifs_server_lock(server);
+		scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
+		cifs_server_unlock(server);
+		rc = ops->tree_connect(xid, tcon->ses, tree,
+				       tcon, tcon->ses->local_nls);
+		goto out;
+	}
+
+	sb = cifs_get_dfs_tcon_super(tcon);
+	if (!IS_ERR(sb))
+		cifs_sb = CIFS_SB(sb);
+
+	/* Tree connect to last share in @tcon->tree_name if no DFS referral */
+	if (!server->leaf_fullpath ||
+	    dfs_cache_noreq_find(server->leaf_fullpath + 1, &ref, &tl)) {
+		rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name,
+				       tcon, tcon->ses->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;
+		tcon->need_reconnect = false;
+		spin_unlock(&tcon->tc_lock);
+	}
+
+	return rc;
+}