SUNRPC,RPCSEC_GSS: fix krb5 sequence numbers.

Use a spinlock to ensure unique sequence numbers when creating krb5 gss tokens.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/auth_gss/gss_krb5_seal.c b/net/sunrpc/auth_gss/gss_krb5_seal.c
index 58f9721..f433112 100644
--- a/net/sunrpc/auth_gss/gss_krb5_seal.c
+++ b/net/sunrpc/auth_gss/gss_krb5_seal.c
@@ -70,6 +70,8 @@
 # define RPCDBG_FACILITY        RPCDBG_AUTH
 #endif
 
+spinlock_t krb5_seq_lock = SPIN_LOCK_UNLOCKED;
+
 u32
 gss_get_mic_kerberos(struct gss_ctx *gss_ctx, struct xdr_buf *text,
 		struct xdr_netobj *token)
@@ -80,6 +82,7 @@
 	struct xdr_netobj	md5cksum = {.len = 0, .data = cksumdata};
 	unsigned char		*ptr, *krb5_hdr, *msg_start;
 	s32			now;
+	u32			seq_send;
 
 	dprintk("RPC:     gss_krb5_seal\n");
 
@@ -134,11 +137,13 @@
 		BUG();
 	}
 
-	if ((krb5_make_seq_num(ctx->seq, ctx->initiate ? 0 : 0xff,
-			       ctx->seq_send, krb5_hdr + 16, krb5_hdr + 8)))
-		goto out_err;
+	spin_lock(&krb5_seq_lock);
+	seq_send = ctx->seq_send++;
+	spin_unlock(&krb5_seq_lock);
 
-	ctx->seq_send++;
+	if ((krb5_make_seq_num(ctx->seq, ctx->initiate ? 0 : 0xff,
+			       seq_send, krb5_hdr + 16, krb5_hdr + 8)))
+		goto out_err;
 
 	return ((ctx->endtime < now) ? GSS_S_CONTEXT_EXPIRED : GSS_S_COMPLETE);
 out_err: