[CIFS] possible memory corruption on mount

CIFS cleanup_volume_info_contents() looks like having a memory
corruption problem.
When UNCip is set to "&vol->UNC[2]" in cifs_parse_mount_options(), it
should not be kfree()-ed in cleanup_volume_info_contents().

Introduced in commit b946845aSigned-off-by: NJ.R. Okajima <hooanon05@yahoo.co.jp>
Reviewed-by: NJeff Layton <jlayton@redhat.com>
CC: Stable <stable@kernel.org>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

fs/cifs/connect.c

@@ -2878,7 +2878,8 @@ cleanup_volume_info_contents(struct smb_vol *volume_info)
 	kfree(volume_info->username);
 	kzfree(volume_info->password);
 	kfree(volume_info->UNC);
-	kfree(volume_info->UNCip);
+	if (volume_info->UNCip != volume_info->UNC + 2)
+		kfree(volume_info->UNCip);
 	kfree(volume_info->domainname);
 	kfree(volume_info->iocharset);
 	kfree(volume_info->prepath);