[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>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index 3188e4d9cddb..b537fad3bf50 100644
--- a/fs/cifs/sess.c
+++ b/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)) {