From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:33566 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1424383AbeE1LOP (ORCPT ); Mon, 28 May 2018 07:14:15 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Niklas Cassel , "David S. Miller" , Sasha Levin Subject: [PATCH 4.16 225/272] net: stmmac: ensure that the device has released ownership before reading data Date: Mon, 28 May 2018 12:04:18 +0200 Message-Id: <20180528100259.327672167@linuxfoundation.org> In-Reply-To: <20180528100240.256525891@linuxfoundation.org> References: <20180528100240.256525891@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Niklas Cassel [ Upstream commit a6b25da5e7ba212af5826a662e6a035a79bffabd ] According to Documentation/memory-barriers.txt, we need to use a dma_rmb() after reading the status/own bit, to ensure that all descriptor fields are read after reading the own bit. This way, we ensure that the DMA engine is done with the DMA descriptor before we read the other descriptor fields, e.g. reading the tx hardware timestamp (if PTP is enabled). Signed-off-by: Niklas Cassel Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -1843,6 +1843,11 @@ static void stmmac_tx_clean(struct stmma if (unlikely(status & tx_dma_own)) break; + /* Make sure descriptor fields are read after reading + * the own bit. + */ + dma_rmb(); + /* Just consider the last segment and ...*/ if (likely(!(status & tx_not_ls))) { /* ... verify the status error condition */