| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Thu, 16 Jan 2020 18:03:26 +0000
From: Andre Przywara <andre.przywara@....com>
To: Radhey Shyam Pandey <radheys@...inx.com>
Cc: "David S . Miller" <davem@...emloft.net>,
Michal Simek <michals@...inx.com>,
Robert Hancock <hancock@...systems.ca>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/14] net: axienet: Fix DMA descriptor cleanup path
On Fri, 10 Jan 2020 17:05:45 +0000
Radhey Shyam Pandey <radheys@...inx.com> wrote:
Hi,
> > -----Original Message-----
> > From: Andre Przywara <andre.przywara@....com>
> > Sent: Friday, January 10, 2020 9:13 PM
> > To: Radhey Shyam Pandey <radheys@...inx.com>
> > Cc: David S . Miller <davem@...emloft.net>; Michal Simek
> > <michals@...inx.com>; Robert Hancock <hancock@...systems.ca>;
> > netdev@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> > kernel@...r.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 <radheys@...inx.com> wrote:
> >
> > Hi Radhey,
> >
> > thanks for having a look!
> >
> > > > -----Original Message-----
> > > > From: Andre Przywara <andre.przywara@....com>
> > > > Sent: Friday, January 10, 2020 5:24 PM
> > > > To: David S . Miller <davem@...emloft.net>; Radhey Shyam Pandey
> > > > <radheys@...inx.com>
> > > > Cc: Michal Simek <michals@...inx.com>; Robert Hancock
> > > > <hancock@...systems.ca>; netdev@...r.kernel.org; linux-arm-
> > > > kernel@...ts.infradead.org; linux-kernel@...r.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 <andre.przywara@....com>
> > > > ---
> > > > .../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
> > >
>
Powered by blists - more mailing lists