cifs: fix crash in cifs_dfs_do_automount

RHBZ: 1649907

Fix a crash that happens while attempting to mount a DFS referral from the same server on the root of a filesystem.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 8ad8bbe8003b..6331c4f93b59 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -4484,11 +4484,13 @@ cifs_are_all_path_components_accessible(struct TCP_Server_Info *server,
                                         unsigned int xid,
                                         struct cifs_tcon *tcon,
                                         struct cifs_sb_info *cifs_sb,
-                                        char *full_path)
+                                        char *full_path,
+                                        int added_treename)
 {
         int rc;
         char *s;
         char sep, tmp;
+        int skip = added_treename ? 1 : 0;
 
         sep = CIFS_DIR_SEP(cifs_sb);
         s = full_path;
@@ -4503,7 +4505,14 @@ cifs_are_all_path_components_accessible(struct TCP_Server_Info *server,
                 /* next separator */
                 while (*s && *s != sep)
                         s++;
-
+                /*
+                 * if the treename is added, we then have to skip the first
+                 * part within the separators
+                 */
+                if (skip) {
+                        skip = 0;
+                        continue;
+                }
                 /*
                  * temporarily null-terminate the path at the end of
                  * the current component
@@ -4551,8 +4560,7 @@ static int is_path_remote(struct cifs_sb_info *cifs_sb, struct smb_vol *vol,
 
         if (rc != -EREMOTE) {
                 rc = cifs_are_all_path_components_accessible(server, xid, tcon,
-                                                             cifs_sb,
-                                                             full_path);
+                        cifs_sb, full_path, tcon->Flags & SMB_SHARE_IS_IN_DFS);
                 if (rc != 0) {
                         cifs_dbg(VFS, "cannot query dirs between root and final path, "
                                  "enabling CIFS_MOUNT_USE_PREFIX_PATH\n");