cifs: fix error handling in mount-time DFS referral chasing code

If the referral is malformed or the hostname can't be resolved, then
the current code generates an oops. Fix it to handle these errors
gracefully.

Reported-by: Sandro Mathys <sm@sandro-mathys.ch>
Acked-by: Igor Mammedov <niallain@gmail.com>
CC: Stable <stable@kernel.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index fc44d316d0bb..f2486889b7bb 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2544,11 +2544,20 @@ remote_path_check:
 
                         if (mount_data != mount_data_global)
                                 kfree(mount_data);
+
                         mount_data = cifs_compose_mount_options(
                                         cifs_sb->mountdata, full_path + 1,
                                         referrals, &fake_devname);
-                        kfree(fake_devname);
+
                         free_dfs_info_array(referrals, num_referrals);
+                        kfree(fake_devname);
+                        kfree(full_path);
+
+                        if (IS_ERR(mount_data)) {
+                                rc = PTR_ERR(mount_data);
+                                mount_data = NULL;
+                                goto mount_fail_check;
+                        }
 
                         if (tcon)
                                 cifs_put_tcon(tcon);
@@ -2556,8 +2565,6 @@ remote_path_check:
                                 cifs_put_smb_ses(pSesInfo);
 
                         cleanup_volume_info(&volume_info);
-                        FreeXid(xid);
-                        kfree(full_path);
                         referral_walks_count++;
                         goto try_mount_again;
                 }