iw_cxgb4: fix ECN check on the passive accept

pass_accept_req() is using the same skb for handling accept request and
sending accept reply to HW. Here req and rpl structures are pointing to
same skb->data which is over written by INIT_TP_WR() and leads to
accessing corrupt req fields in accept_cr() while checking for ECN flags.
Reordered code in accept_cr() to fetch correct req fields.

Fixes: 92e7ae7 ("iw_cxgb4: Choose appropriate hw mtu index and ISS for iWARP connections")
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Link: https://lore.kernel.org/r/20191003104353.11590-1-bharat@chelsio.com
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/cxgb4/cm.c

@@ -2424,20 +2424,6 @@ static int accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
 	enum chip_type adapter_type = ep->com.dev->rdev.lldi.adapter_type;
 
 	pr_debug("ep %p tid %u\n", ep, ep->hwtid);
-
-	skb_get(skb);
-	rpl = cplhdr(skb);
-	if (!is_t4(adapter_type)) {
-		skb_trim(skb, roundup(sizeof(*rpl5), 16));
-		rpl5 = (void *)rpl;
-		INIT_TP_WR(rpl5, ep->hwtid);
-	} else {
-		skb_trim(skb, sizeof(*rpl));
-		INIT_TP_WR(rpl, ep->hwtid);
-	}
-	OPCODE_TID(rpl) = cpu_to_be32(MK_OPCODE_TID(CPL_PASS_ACCEPT_RPL,
-						    ep->hwtid));
-
 	cxgb_best_mtu(ep->com.dev->rdev.lldi.mtus, ep->mtu, &mtu_idx,
 		      enable_tcp_timestamps && req->tcpopt.tstamp,
 		      (ep->com.remote_addr.ss_family == AF_INET) ? 0 : 1);
@@ -2483,6 +2469,20 @@ static int accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
 		if (tcph->ece && tcph->cwr)
 			opt2 |= CCTRL_ECN_V(1);
 	}
+
+	skb_get(skb);
+	rpl = cplhdr(skb);
+	if (!is_t4(adapter_type)) {
+		skb_trim(skb, roundup(sizeof(*rpl5), 16));
+		rpl5 = (void *)rpl;
+		INIT_TP_WR(rpl5, ep->hwtid);
+	} else {
+		skb_trim(skb, sizeof(*rpl));
+		INIT_TP_WR(rpl, ep->hwtid);
+	}
+	OPCODE_TID(rpl) = cpu_to_be32(MK_OPCODE_TID(CPL_PASS_ACCEPT_RPL,
+						    ep->hwtid));
+
 	if (CHELSIO_CHIP_VERSION(adapter_type) > CHELSIO_T4) {
 		u32 isn = (prandom_u32() & ~7UL) - 1;
 		opt2 |= T5_OPT_2_VALID_F;