linux-kernel - [PATCH 4.9 129/223] bnx2x: Prevent load reordering in tx completion processing

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Message-Id: <20190802092247.364104604@linuxfoundation.org>
Date:   Fri,  2 Aug 2019 11:35:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Brian King <brking@...ux.vnet.ibm.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 129/223] bnx2x: Prevent load reordering in tx completion processing

From: Brian King <brking@...ux.vnet.ibm.com>

[ Upstream commit ea811b795df24644a8eb760b493c43fba4450677 ]

This patch fixes an issue seen on Power systems with bnx2x which results
in the skb is NULL WARN_ON in bnx2x_free_tx_pkt firing due to the skb
pointer getting loaded in bnx2x_free_tx_pkt prior to the hw_cons
load in bnx2x_tx_int. Adding a read memory barrier resolves the issue.

Signed-off-by: Brian King <brking@...ux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.c
@@ -286,6 +286,9 @@ int bnx2x_tx_int(struct bnx2x *bp, struc
 	hw_cons = le16_to_cpu(*txdata->tx_cons_sb);
 	sw_cons = txdata->tx_pkt_cons;
 
+	/* Ensure subsequent loads occur after hw_cons */
+	smp_rmb();
+
 	while (sw_cons != hw_cons) {
 		u16 pkt_cons;