From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50F4BC33CAF for ; Thu, 16 Jan 2020 18:03:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DE672192A for ; Thu, 16 Jan 2020 18:03:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406900AbgAPSDf (ORCPT ); Thu, 16 Jan 2020 13:03:35 -0500 Received: from foss.arm.com ([217.140.110.172]:56900 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393641AbgAPSDe (ORCPT ); Thu, 16 Jan 2020 13:03:34 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DF3BD31B; Thu, 16 Jan 2020 10:03:33 -0800 (PST) Received: from donnerap.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DE2C73F534; Thu, 16 Jan 2020 10:03:32 -0800 (PST) Date: Thu, 16 Jan 2020 18:03:26 +0000 From: Andre Przywara To: Radhey Shyam Pandey Cc: "David S . Miller" , Michal Simek , Robert Hancock , "netdev@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 03/14] net: axienet: Fix DMA descriptor cleanup path Message-ID: <20200116180326.47c93ce2@donnerap.cambridge.arm.com> In-Reply-To: References: <20200110115415.75683-1-andre.przywara@arm.com> <20200110115415.75683-4-andre.przywara@arm.com> <20200110154328.6676215f@donnerap.cambridge.arm.com> Organization: ARM X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; aarch64-unknown-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 10 Jan 2020 17:05:45 +0000 Radhey Shyam Pandey wrote: Hi, > > -----Original Message----- > > From: Andre Przywara > > Sent: Friday, January 10, 2020 9:13 PM > > To: Radhey Shyam Pandey > > Cc: David S . Miller ; Michal Simek > > ; Robert Hancock ; > > netdev@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux- > > kernel@vger.kernel.org > > Subject: Re: [PATCH 03/14] net: axienet: Fix DMA descriptor cleanup path > > > > On Fri, 10 Jan 2020 15:14:46 +0000 > > Radhey Shyam Pandey wrote: > > > > Hi Radhey, > > > > thanks for having a look! > > > > > > -----Original Message----- > > > > From: Andre Przywara > > > > Sent: Friday, January 10, 2020 5:24 PM > > > > To: David S . Miller ; Radhey Shyam Pandey > > > > > > > > Cc: Michal Simek ; Robert Hancock > > > > ; netdev@vger.kernel.org; linux-arm- > > > > kernel@lists.infradead.org; linux-kernel@vger.kernel.org > > > > Subject: [PATCH 03/14] net: axienet: Fix DMA descriptor cleanup path > > > > > > > > When axienet_dma_bd_init() bails out during the initialisation process, > > > > it might do so with parts of the structure already allocated and > > > > initialised, while other parts have not been touched yet. Before > > > > returning in this case, we call axienet_dma_bd_release(), which does not > > > > take care of this corner case. > > > > This is most obvious by the first loop happily dereferencing > > > > lp->rx_bd_v, which we actually check to be non NULL *afterwards*. > > > > > > > > Make sure we only unmap or free already allocated structures, by: > > > > - directly returning with -ENOMEM if nothing has been allocated at all > > > > - checking for lp->rx_bd_v to be non-NULL *before* using it > > > > - only unmapping allocated DMA RX regions > > > > > > > > This avoids NULL pointer dereferences when initialisation fails. > > > > > > > > Signed-off-by: Andre Przywara > > > > --- > > > > .../net/ethernet/xilinx/xilinx_axienet_main.c | 43 ++++++++++++------- > > > > 1 file changed, 28 insertions(+), 15 deletions(-) > > > > > > > > diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > > > > b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > > > > index 97482cf093ce..7e90044cf2d9 100644 > > > > --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > > > > +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c > > > > @@ -160,24 +160,37 @@ static void axienet_dma_bd_release(struct > > > > net_device *ndev) > > > > int i; > > > > struct axienet_local *lp = netdev_priv(ndev); > > > > > > > > + /* If we end up here, tx_bd_v must have been DMA allocated. */ > > > > + dma_free_coherent(ndev->dev.parent, > > > > + sizeof(*lp->tx_bd_v) * lp->tx_bd_num, > > > > + lp->tx_bd_v, > > > > + lp->tx_bd_p); > > > > + > > > > + if (!lp->rx_bd_v) > > > > + return; > > > > + > > > > for (i = 0; i < lp->rx_bd_num; i++) { > > > > - dma_unmap_single(ndev->dev.parent, lp->rx_bd_v[i].phys, > > > > - lp->max_frm_size, DMA_FROM_DEVICE); > > > > + /* A NULL skb means this descriptor has not been initialised > > > > + * at all. > > > > + */ > > > > + if (!lp->rx_bd_v[i].skb) > > > > + break; > > > > + > > > > dev_kfree_skb(lp->rx_bd_v[i].skb); > > > > - } > > > > > > > > - if (lp->rx_bd_v) { > > > > - dma_free_coherent(ndev->dev.parent, > > > > - sizeof(*lp->rx_bd_v) * lp->rx_bd_num, > > > > - lp->rx_bd_v, > > > > - lp->rx_bd_p); > > > > - } > > > > - if (lp->tx_bd_v) { > > > > - dma_free_coherent(ndev->dev.parent, > > > > - sizeof(*lp->tx_bd_v) * lp->tx_bd_num, > > > > - lp->tx_bd_v, > > > > - lp->tx_bd_p); > > > > + /* For each descriptor, we programmed cntrl with the (non- > > > > zero) > > > > + * descriptor size, after it had been successfully allocated. > > > > + * So a non-zero value in there means we need to unmap it. > > > > + */ > > > > > > > + if (lp->rx_bd_v[i].cntrl) > > > > > > I think it should ok to unmap w/o any check? > > > > Do you mean because .phys would be 0 if not initialised? AFAIK 0 can be a > > valid DMA address, so there is no special check for that, and unmapping > > DMA address 0 will probably go wrong at some point. So it's unlike > > kfree(NULL). > > I mean if skb allocation is successful in _dma_bd_init then in release path > we can assume .phys is always a valid address and skip rx_bd_v[i].cntrl > check. I don't think we can assume this. If the skb allocation succeeded, but then the dma_map_single failed (which we check with dma_mapping_error()), we would end up with a valid skb, but an uninitialised phys DMA address in the registers. That's why I set .cntrl only after having checked the dma_map_single() result. Or am I missing something? Cheers, Andre > > > > + dma_unmap_single(ndev->dev.parent, lp- > > > > >rx_bd_v[i].phys, > > > > + lp->max_frm_size, > > > > DMA_FROM_DEVICE); > > > > } > > > > + > > > > + dma_free_coherent(ndev->dev.parent, > > > > + sizeof(*lp->rx_bd_v) * lp->rx_bd_num, > > > > + lp->rx_bd_v, > > > > + lp->rx_bd_p); > > > > } > > > > > > > > /** > > > > @@ -207,7 +220,7 @@ static int axienet_dma_bd_init(struct net_device > > > > *ndev) > > > > sizeof(*lp->tx_bd_v) * lp- > > > > >tx_bd_num, > > > > &lp->tx_bd_p, GFP_KERNEL); > > > > if (!lp->tx_bd_v) > > > > - goto out; > > > > + return -ENOMEM; > > > > > > > > lp->rx_bd_v = dma_alloc_coherent(ndev->dev.parent, > > > > sizeof(*lp->rx_bd_v) * lp- > > > > >rx_bd_num, > > > > -- > > > > 2.17.1 > > > >