[PATCH 6/7] cifs: Fix retrieval of DFS referrals in cifs_mount()

From: "Paulo Alcantara (SUSE)" <pc@cjr.nz>
To: smfrench@gmail.com
Cc: linux-cifs@vger.kernel.org, "Paulo Alcantara (SUSE)" <pc@cjr.nz>,
	stable@vger.kernel.org,
	Matthew Ruffell <matthew.ruffell@canonical.com>
Subject: [PATCH 6/7] cifs: Fix retrieval of DFS referrals in cifs_mount()
Date: Fri, 22 Nov 2019 12:30:56 -0300	[thread overview]
Message-ID: <20191122153057.6608-7-pc@cjr.nz> (raw)
In-Reply-To: <20191122153057.6608-1-pc@cjr.nz>

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@cjr.nz>
Link: https://lkml.kernel.org/r/05aa2995-e85e-0ff4-d003-5bb08bd17a22@canonical.com
Cc: stable@vger.kernel.org
Tested-by: Matthew Ruffell <matthew.ruffell@canonical.com>
---
 fs/cifs/connect.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 668d477cc9c7..86d98d73749d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -4776,6 +4776,17 @@ 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)
+{
+	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;
@@ -4877,18 +4888,10 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
 	/* 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) {
@@ -4925,6 +4928,15 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
 			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)
-- 
2.24.0

