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Message-ID: <1508645199.29850.16.camel@mtkswgap22>
Date: Sun, 22 Oct 2017 12:06:39 +0800
From: Sean Wang <sean.wang@...iatek.com>
To: "Reshetova, Elena" <elena.reshetova@...el.com>
CC: "davem@...emloft.net" <davem@...emloft.net>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-mediatek@...ts.infradead.org"
<linux-mediatek@...ts.infradead.org>,
"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
"linux-hams@...r.kernel.org" <linux-hams@...r.kernel.org>,
"linux-ppp@...r.kernel.org" <linux-ppp@...r.kernel.org>,
"ganeshgr@...lsio.com" <ganeshgr@...lsio.com>,
"nbd@...nwrt.org" <nbd@...nwrt.org>,
"john@...ozen.org" <john@...ozen.org>,
"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
"yishaih@...lanox.com" <yishaih@...lanox.com>,
"saeedm@...lanox.com" <saeedm@...lanox.com>,
"matanb@...lanox.com" <matanb@...lanox.com>,
"tariqt@...lanox.com" <tariqt@...lanox.com>,
"leonro@...lanox.com" <leonro@...lanox.com>,
"ajk@...nets.uni-bremen.de" <ajk@...nets.uni-bremen.de>,
"paulus@...ba.org" <paulus@...ba.org>,
"zbr@...emap.net" <zbr@...emap.net>,
"peterz@...radead.org" <peterz@...radead.org>,
"keescook@...omium.org" <keescook@...omium.org>
Subject: RE: [PATCH 02/15] drivers, net, ethernet: convert
mtk_eth.dma_refcnt from atomic_t to refcount_t
On Fri, 2017-10-20 at 10:37 +0000, Reshetova, Elena wrote:
> > On Fri, 2017-10-20 at 10:23 +0300, Elena Reshetova wrote:
> > > atomic_t variables are currently used to implement reference
> > > counters with the following properties:
> > > - counter is initialized to 1 using atomic_set()
> > > - a resource is freed upon counter reaching zero
> > > - once counter reaches zero, its further
> > > increments aren't allowed
> > > - counter schema uses basic atomic operations
> > > (set, inc, inc_not_zero, dec_and_test, etc.)
> > >
> > > Such atomic variables should be converted to a newly provided
> > > refcount_t type and API that prevents accidental counter overflows
> > > and underflows. This is important since overflows and underflows
> > > can lead to use-after-free situation and be exploitable.
> > >
> > > The variable mtk_eth.dma_refcnt is used as pure reference counter.
> > > Convert it to refcount_t and fix up the operations.
> > >
> > > Suggested-by: Kees Cook <keescook@...omium.org>
> > > Reviewed-by: David Windsor <dwindsor@...il.com>
> > > Reviewed-by: Hans Liljestrand <ishkamiel@...il.com>
> > > Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> > > ---
> > > drivers/net/ethernet/mediatek/mtk_eth_soc.c | 8 +++++---
> > > drivers/net/ethernet/mediatek/mtk_eth_soc.h | 4 +++-
> > > 2 files changed, 8 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > > index 5e81a72..54adfd9 100644
> > > --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > > +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > > @@ -1817,7 +1817,7 @@ static int mtk_open(struct net_device *dev)
> > > struct mtk_eth *eth = mac->hw;
> > >
> > > /* we run 2 netdevs on the same dma ring so we only bring it up once
> > */
> > > - if (!atomic_read(ð->dma_refcnt)) {
> > > + if (!refcount_read(ð->dma_refcnt)) {
> > > int err = mtk_start_dma(eth);
> > >
> > > if (err)
> > > @@ -1827,8 +1827,10 @@ static int mtk_open(struct net_device *dev)
> > > napi_enable(ð->rx_napi);
> > > mtk_tx_irq_enable(eth, MTK_TX_DONE_INT);
> > > mtk_rx_irq_enable(eth, MTK_RX_DONE_INT);
> > > + refcount_set(ð->dma_refcnt, 1);
> >
> > the existing driver seems to have a missing initial atomic_set for the
> > eth->dma_refcnt.
> >
> > > }
> > > - atomic_inc(ð->dma_refcnt);
> > > + else
> > > + refcount_inc(ð->dma_refcnt);
> > >
> >
> > how about add the initial refcount_set into probe handler, and keep
> > logic else unchanged ?
>
> Sure, I guess you mean mtk_probe() function? I can move the refcount_set to be there
> and remove this change.
>
> Should I resend the modified patch to you (maybe then two of the ethernet patches)?
>
> Best Regards,
> Elena.
The entire series has been applies to net-next, I think I can make the
follow-ups patches relative to your work.
Sean
> >
> > > phy_start(dev->phydev);
> > > netif_start_queue(dev);
> > > @@ -1868,7 +1870,7 @@ static int mtk_stop(struct net_device *dev)
> > > phy_stop(dev->phydev);
> > >
> > > /* only shutdown DMA if this is the last user */
> > > - if (!atomic_dec_and_test(ð->dma_refcnt))
> > > + if (!refcount_dec_and_test(ð->dma_refcnt))
> > > return 0;
> > >
> > > mtk_tx_irq_disable(eth, MTK_TX_DONE_INT);
> > > diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
> > b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
> > > index 3d3c24a..a3af466 100644
> > > --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.h
> > > +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.h
> > > @@ -15,6 +15,8 @@
> > > #ifndef MTK_ETH_H
> > > #define MTK_ETH_H
> > >
> > > +#include <linux/refcount.h>
> > > +
> > > #define MTK_QDMA_PAGE_SIZE 2048
> > > #define MTK_MAX_RX_LENGTH 1536
> > > #define MTK_TX_DMA_BUF_LEN 0x3fff
> > > @@ -632,7 +634,7 @@ struct mtk_eth {
> > > struct regmap *pctl;
> > > u32 chip_id;
> > > bool hwlro;
> > > - atomic_t dma_refcnt;
> > > + refcount_t dma_refcnt;
> > > struct mtk_tx_ring tx_ring;
> > > struct mtk_rx_ring
> > rx_ring[MTK_MAX_RX_RING_NUM];
> > > struct mtk_rx_ring rx_ring_qdma;
> >
>
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