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From: Leon Romanovsky <leon@kernel.org>
To: Ivan Vecera <ivecera@redhat.com>
Cc: Michal Schmidt <mschmidt@redhat.com>,
	netdev@vger.kernel.org, Petr Oros <poros@redhat.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Tony Nguyen <anthony.l.nguyen@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Shiraz Saleem <shiraz.saleem@intel.com>,
	Dave Ertman <david.m.ertman@intel.com>,
	"moderated list:INTEL ETHERNET DRIVERS" 
	<intel-wired-lan@lists.osuosl.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] ice: Fix race during aux device (un)plugging
Date: Wed, 20 Apr 2022 09:36:43 +0300	[thread overview]
Message-ID: <Yl+p+7C7JQDj1jt1@unreal> (raw)
In-Reply-To: <20220415174932.6c85d5ab@ceranb>

On Fri, Apr 15, 2022 at 05:49:32PM +0200, Ivan Vecera wrote:
> On Fri, 15 Apr 2022 13:12:03 +0200
> Michal Schmidt <mschmidt@redhat.com> wrote:
> 
> > On Thu, Apr 14, 2022 at 6:39 PM Ivan Vecera <ivecera@redhat.com> wrote:
> > 
> > > Function ice_plug_aux_dev() assigns pf->adev field too early prior
> > > aux device initialization and on other side ice_unplug_aux_dev()
> > > starts aux device deinit and at the end assigns NULL to pf->adev.
> > > This is wrong and can causes a crash when ice_send_event_to_aux()
> > > call occurs during these operations because that function depends
> > > on non-NULL value of pf->adev and does not assume that aux device
> > > is half-initialized or half-destroyed.
> > >
> > > Modify affected functions so pf->adev field is set after aux device
> > > init and prior aux device destroy.
> > >  
> > [...]
> > 
> > > @@ -320,12 +319,14 @@ int ice_plug_aux_dev(struct ice_pf *pf)
> > >   */
> > >  void ice_unplug_aux_dev(struct ice_pf *pf)
> > >  {
> > > -       if (!pf->adev)
> > > +       struct auxiliary_device *adev = pf->adev;
> > > +
> > > +       if (!adev)
> > >                 return;
> > >
> > > -       auxiliary_device_delete(pf->adev);
> > > -       auxiliary_device_uninit(pf->adev);
> > >         pf->adev = NULL;
> > > +       auxiliary_device_delete(adev);
> > > +       auxiliary_device_uninit(adev);
> > >  }
> > >  
> > 
> > Hi Ivan,
> > What prevents ice_unplug_aux_dev() from running immediately after
> > ice_send_event_to_aux() gets past its "if (!pf->adev)" test ?
> > Michal
> 
> ice_send_event_to_aux() takes aux device lock. ice_unplug_aux_dev()
> calls auxiliary_device_delete() that calls device_del(). device_del()
> takes device_lock() prior kill_device(). So if ice_send_event_to_aux()
> is in progress then device_del() waits for its completion.

Not really, you nullify pf->adev without any lock protection and
ice_send_event_to_aux() will simply crash.

 CPU#1          	|   CPU#2
			| ice_send_event_to_aux
 ice_unplug_aux_dev()   | ...
 ...                    | 
 pf->adev = NULL;       | 
      			| device_lock(&pf->adev->dev); <--- crash here.

Thanks


> 
> Thanks,
> Ivan
> 

WARNING: multiple messages have this Message-ID (diff)
From: Leon Romanovsky <leon@kernel.org>
To: intel-wired-lan@osuosl.org
Subject: [Intel-wired-lan] [PATCH net] ice: Fix race during aux device (un)plugging
Date: Wed, 20 Apr 2022 09:36:43 +0300	[thread overview]
Message-ID: <Yl+p+7C7JQDj1jt1@unreal> (raw)
In-Reply-To: <20220415174932.6c85d5ab@ceranb>

On Fri, Apr 15, 2022 at 05:49:32PM +0200, Ivan Vecera wrote:
> On Fri, 15 Apr 2022 13:12:03 +0200
> Michal Schmidt <mschmidt@redhat.com> wrote:
> 
> > On Thu, Apr 14, 2022 at 6:39 PM Ivan Vecera <ivecera@redhat.com> wrote:
> > 
> > > Function ice_plug_aux_dev() assigns pf->adev field too early prior
> > > aux device initialization and on other side ice_unplug_aux_dev()
> > > starts aux device deinit and at the end assigns NULL to pf->adev.
> > > This is wrong and can causes a crash when ice_send_event_to_aux()
> > > call occurs during these operations because that function depends
> > > on non-NULL value of pf->adev and does not assume that aux device
> > > is half-initialized or half-destroyed.
> > >
> > > Modify affected functions so pf->adev field is set after aux device
> > > init and prior aux device destroy.
> > >  
> > [...]
> > 
> > > @@ -320,12 +319,14 @@ int ice_plug_aux_dev(struct ice_pf *pf)
> > >   */
> > >  void ice_unplug_aux_dev(struct ice_pf *pf)
> > >  {
> > > -       if (!pf->adev)
> > > +       struct auxiliary_device *adev = pf->adev;
> > > +
> > > +       if (!adev)
> > >                 return;
> > >
> > > -       auxiliary_device_delete(pf->adev);
> > > -       auxiliary_device_uninit(pf->adev);
> > >         pf->adev = NULL;
> > > +       auxiliary_device_delete(adev);
> > > +       auxiliary_device_uninit(adev);
> > >  }
> > >  
> > 
> > Hi Ivan,
> > What prevents ice_unplug_aux_dev() from running immediately after
> > ice_send_event_to_aux() gets past its "if (!pf->adev)" test ?
> > Michal
> 
> ice_send_event_to_aux() takes aux device lock. ice_unplug_aux_dev()
> calls auxiliary_device_delete() that calls device_del(). device_del()
> takes device_lock() prior kill_device(). So if ice_send_event_to_aux()
> is in progress then device_del() waits for its completion.

Not really, you nullify pf->adev without any lock protection and
ice_send_event_to_aux() will simply crash.

 CPU#1          	|   CPU#2
			| ice_send_event_to_aux
 ice_unplug_aux_dev()   | ...
 ...                    | 
 pf->adev = NULL;       | 
      			| device_lock(&pf->adev->dev); <--- crash here.

Thanks


> 
> Thanks,
> Ivan
> 

  parent reply	other threads:[~2022-04-20  6:37 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-14 16:39 [PATCH net] ice: Fix race during aux device (un)plugging Ivan Vecera
2022-04-14 16:39 ` [Intel-wired-lan] " Ivan Vecera
2022-04-15 11:12 ` Michal Schmidt
2022-04-15 15:49   ` Ivan Vecera
2022-04-15 15:49     ` [Intel-wired-lan] " Ivan Vecera
2022-04-15 17:53     ` Ertman, David M
2022-04-15 17:53       ` [Intel-wired-lan] " Ertman, David M
2022-04-20  6:36     ` Leon Romanovsky [this message]
2022-04-20  6:36       ` Leon Romanovsky
2022-04-20 13:59       ` Ivan Vecera

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