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Date: Thu, 18 Apr 2019 18:17:09 +0000
From: Saeed Mahameed <saeedm@...lanox.com>
To: "sathya.perla@...adcom.com" <sathya.perla@...adcom.com>,
"sriharsha.basavapatna@...adcom.com"
<sriharsha.basavapatna@...adcom.com>,
"fyang@...e.com" <fyang@...e.com>,
"somnath.kotur@...adcom.com" <somnath.kotur@...adcom.com>,
"ajit.khaparde@...adcom.com" <ajit.khaparde@...adcom.com>,
"davem@...emloft.net" <davem@...emloft.net>
CC: "firogm@...il.com" <firogm@...il.com>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/1] be2net: Detach interface for avoiding a system crash
On Thu, 2019-04-18 at 15:05 +0800, Firo wrote:
>
> On 4/2/19 12:25 AM, Saeed Mahameed wrote:
> > On Mon, 2019-04-01 at 20:24 +0800, Firo Yang wrote:
> > > This crash is triggered by a user-after-free since lake of
> > > the synchronization of a race condition between
> > > be_update_queues() modifying multi-purpose channels of
> > > network device and be_tx_timeout().
> > >
> > > BUG: unable to handle kernel NULL pointer dereference at (null)
> > > Call Trace:
> > > be_tx_timeout+0xa5/0x360 [be2net]
> > > dev_watchdog+0x1d8/0x210
> > > call_timer_fn+0x32/0x140
> > >
> > > To fix it, detach the interface before modifying
> > > multi-purpose channels of network device.
> > >
> > > Signed-off-by: Firo Yang <fyang@...e.com>
> > > ---
> > > drivers/net/ethernet/emulex/benet/be_main.c | 12 ++++++++----
> > > 1 file changed, 8 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/emulex/benet/be_main.c
> > > b/drivers/net/ethernet/emulex/benet/be_main.c
> > > index d5026909dec5..25d0128bf684 100644
> > > --- a/drivers/net/ethernet/emulex/benet/be_main.c
> > > +++ b/drivers/net/ethernet/emulex/benet/be_main.c
> > > @@ -4705,6 +4705,8 @@ int be_update_queues(struct be_adapter
> > > *adapter)
> > > struct net_device *netdev = adapter->netdev;
> > > int status;
> > >
> > > + netif_device_detach(netdev);
> > > +
> >
> > This will reduce the probability, but will not do the trick.
> > since this will not guarantee that the dev_watchdog is disabled.
> Hi Saeed,
>
> What about using dev_watchdog_down/up() to temporarily disable the
> dev_watchdog?
>
> +++ b/drivers/net/ethernet/emulex/benet/be_main.c
> @@ -4697,6 +4697,8 @@ int be_update_queues(struct be_adapter
> *adapter)
> struct net_device *netdev = adapter->netdev;
> int status;
>
> + dev_watchdog_down();
> +
there is no such API, currently this is a static function, and i don't
think it is a good idea to mess around with the watchdog.
If you want to avoid deferred work and explicit locking, you need
something similar to what you did with the device_detach to flag to the
watchdog to not look at your tx queues.
by looking at be_close() I see that it calls netif_tx_disable(netdev);
which provides some kind of state synchronization with the watchdog.
so maybe netif_device_detach() will work, but it is a very heavy gun!
netif_carrier_off(netdev) should do the work, and at the end you will
need to restore the original carrier state.
carrier_ok = netif_carrier_ok(netdev);
/* must be called before netif_tx_disable() */
netif_carrier_off(netdev);
// do stuff
if (carrier_ok)
netif_carrier_on(netdev);
> if (netif_running(netdev))
> be_close(netdev);
>
> @@ -4711,21 +4713,21 @@ int be_update_queues(struct be_adapter
> *adapter)
> be_clear_queues(adapter);
> status = be_cmd_if_destroy(adapter, adapter->if_handle, 0);
> if (status)
> - return status;
> + goto out;
>
> if (!msix_enabled(adapter)) {
> status = be_msix_enable(adapter);
> if (status)
> - return status;
> + goto out;
> }
>
> status = be_if_create(adapter);
> if (status)
> - return status;
> + goto out;
>
> status = be_setup_queues(adapter);
> if (status)
> - return status;
> + goto out;
>
> be_schedule_worker(adapter);
>
> @@ -4741,6 +4743,9 @@ int be_update_queues(struct be_adapter
> *adapter)
> if (netif_running(netdev))
> status = be_open(netdev);
>
> +out:
> + dev_watchdog_up();
>
> Thanks,
> Firo
>
> > what you need is proper locking mechanism and/or scheduling the
> > tx_timeout handling out of atomic context if a mutex will be
> > required.
> >
> > netif_device_detach is a too heavy hammer for such synchronizations
> > tasks.
> >
> > > if (netif_running(netdev))
> > > be_close(netdev);
> > >
> > > @@ -4719,21 +4721,21 @@ int be_update_queues(struct be_adapter
> > > *adapter)
> > > be_clear_queues(adapter);
> > > status = be_cmd_if_destroy(adapter, adapter->if_handle, 0);
> > > if (status)
> > > - return status;
> > > + goto out;
> > >
> > > if (!msix_enabled(adapter)) {
> > > status = be_msix_enable(adapter);
> > > if (status)
> > > - return status;
> > > + goto out;
> > > }
> > >
> > > status = be_if_create(adapter);
> > > if (status)
> > > - return status;
> > > + goto out;
> > >
> > > status = be_setup_queues(adapter);
> > > if (status)
> > > - return status;
> > > + goto out;
> > >
> > > be_schedule_worker(adapter);
> > >
> > > @@ -4748,6 +4750,8 @@ int be_update_queues(struct be_adapter
> > > *adapter)
> > > if (netif_running(netdev))
> > > status = be_open(netdev);
> > >
> > > +out:
> > > + netif_device_attach(netdev);
> > > return status;
> > > }
> > >
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