linux-kernel - [PATCH 5.4 38/80] cifs: Fix retrieval of DFS referrals in cifs

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Message-Id: <20191219183107.931508671@linuxfoundation.org>
Date:   Thu, 19 Dec 2019 19:34:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, "Paulo Alcantara (SUSE)" <pc@....nz>,
        Matthew Ruffell <matthew.ruffell@...onical.com>,
        Steve French <stfrench@...rosoft.com>
Subject: [PATCH 5.4 38/80] cifs: Fix retrieval of DFS referrals in cifs_mount()

From: Paulo Alcantara (SUSE) <pc@....nz>

commit 5bb30a4dd60e2a10a4de9932daff23e503f1dd2b upstream.

Make sure that DFS referrals are sent to newly resolved root targets
as in a multi tier DFS setup.

Signed-off-by: Paulo Alcantara (SUSE) <pc@....nz>
Link: https://lkml.kernel.org/r/05aa2995-e85e-0ff4-d003-5bb08bd17a22@canonical.com
Cc: stable@...r.kernel.org
Tested-by: Matthew Ruffell <matthew.ruffell@...onical.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/cifs/connect.c |   32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -4709,6 +4709,17 @@ static int is_path_remote(struct cifs_sb
 }
 
 #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)
+{
+	spin_lock(&cifs_tcp_ses_lock);
+	tcon->tc_count++;
+	tcon->remap = cifs_remap(cifs_sb);
+	spin_unlock(&cifs_tcp_ses_lock);
+	*root = tcon;
+}
+
 int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
 {
 	int rc = 0;
@@ -4810,18 +4821,10 @@ int cifs_mount(struct cifs_sb_info *cifs
 	/* Cache out resolved root server */
 	(void)dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
 			     root_path + 1, NULL, NULL);
-	/*
-	 * Save root tcon for additional DFS requests to update or create a new
-	 * DFS cache entry, or even perform DFS failover.
-	 */
-	spin_lock(&cifs_tcp_ses_lock);
-	tcon->tc_count++;
-	tcon->dfs_path = root_path;
+	kfree(root_path);
 	root_path = NULL;
-	tcon->remap = cifs_remap(cifs_sb);
-	spin_unlock(&cifs_tcp_ses_lock);
 
-	root_tcon = tcon;
+	set_root_tcon(cifs_sb, tcon, &root_tcon);
 
 	for (count = 1; ;) {
 		if (!rc && tcon) {
@@ -4858,6 +4861,15 @@ int cifs_mount(struct cifs_sb_info *cifs
 			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);
+			}
 		}
 		if (rc) {
 			if (rc == -EACCES || rc == -EOPNOTSUPP)