cifs: fix crash in cifs_dfs_do_automount

[ Upstream commit ce465bf94b70f03136171a62b607864f00093b19 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 6ad43ac129d2f49f6406b65532a5368913be062e..18c7c6b2fe08a7e042056da07e753ea52eb1e808 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -4463,11 +4463,13 @@ 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;
@@ -4482,7 +4484,14 @@ 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
@@ -4530,8 +4539,7 @@ 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");