[CIFS] check version in spnego upcall response

Currently, we don't check the version in the SPNEGO upcall response
even though one is provided. Jeff and Q have made the corresponding
change to the Samba client (cifs.upcall).
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/CHANGES

@@ -4,7 +4,11 @@ Fix premature write failure on congested networks (we would give up
 on EAGAIN from the socket too quickly on large writes).
 Cifs_mkdir and cifs_create now respect the setgid bit on parent dir.
 Fix endian problems in acl (mode from/to cifs acl) on bigendian
-architectures.
+architectures.  Fix problems with preserving timestamps on copying open
+files (e.g. "cp -a") to Windows servers.  For mkdir and create honor setgid bit
+on parent directory when server supports Unix Extensions but not POSIX
+create. Update cifs.upcall version to handle new Kerberos sec flags
+(this requires update of cifs.upcall program from Samba).
 
 Version 1.53
 ------------

fs/cifs/cifs_spnego.h

@@ -23,7 +23,7 @@
 #ifndef _CIFS_SPNEGO_H
 #define _CIFS_SPNEGO_H
 
-#define CIFS_SPNEGO_UPCALL_VERSION 1
+#define CIFS_SPNEGO_UPCALL_VERSION 2
 
 /*
  * The version field should always be set to CIFS_SPNEGO_UPCALL_VERSION.

fs/cifs/sess.c

@@ -516,6 +516,15 @@ CIFS_SessSetup(unsigned int xid, struct cifsSesInfo *ses, int first_time,
 		}
 
 		msg = spnego_key->payload.data;
+		/* check version field to make sure that cifs.upcall is
+		   sending us a response in an expected form */
+		if (msg->version != CIFS_SPNEGO_UPCALL_VERSION) {
+			cERROR(1, ("incorrect version of cifs.upcall (expected"
+				   " %d but got %d)",
+				   CIFS_SPNEGO_UPCALL_VERSION, msg->version));
+			rc = -EKEYREJECTED;
+			goto ssetup_exit;
+		}
 		/* bail out if key is too long */
 		if (msg->sesskey_len >
 		    sizeof(ses->server->mac_signing_key.data.krb5)) {