smb: client: ensure to try all targets when finding nested links

With current implementation, when a nested DFS link is found during
mount(2), the client follows the referral and then try to connect to
all of its targets.  If all targets failed, the client bails out
rather than retrying remaining targets from previous referral.

Fix this by stacking all referrals and targets so the client can retry
remaining targets from previous referrals in case all targets of
current referral have failed.

Thanks to samba, this can be easily tested like below

* Run the following under dfs folder in samba server

  $ ln -s "msdfs:srv\\bad-share" link1
  $ ln -s "msdfs:srv\\dfs\\link1,srv\\good-share" link0

* Before patch

  $ mount.cifs //srv/dfs/link0 /mnt -o ...
  mount error(2): No such file or directory
  Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)...

* After patch

  $ mount.cifs //srv/dfs/link0 /mnt -o ...
  # ls /mnt
  bar  fileshare1  sub

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 657dee4b2c8c..712557c2d526 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1721,11 +1721,23 @@ struct cifs_mount_ctx {
 	struct list_head dfs_ses_list;
 };
 
+static inline void __free_dfs_info_param(struct dfs_info3_param *param)
+{
+	kfree(param->path_name);
+	kfree(param->node_name);
+}
+
 static inline void free_dfs_info_param(struct dfs_info3_param *param)
 {
+	if (param)
+		__free_dfs_info_param(param);
+}
+
+static inline void zfree_dfs_info_param(struct dfs_info3_param *param)
+{
 	if (param) {
-		kfree(param->path_name);
-		kfree(param->node_name);
+		__free_dfs_info_param(param);
+		memset(param, 0, sizeof(*param));
 	}
 }