[PATCH v3 10/11] cifs: Fix retrieval of DFS referrals in cifs_mount()

Paulo Alcantara (SUSE)
2019-11-27T00:37:32Z

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