linux-kernel - Re: [Intel-wired-lan] [PATCH net] ice: Fix incorrect locking in ice_vc_process_vf_msg()

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Date:   Thu, 31 Mar 2022 09:32:31 -0700
From:   Brett Creeley <brett@...sando.io>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     Ivan Vecera <ivecera@...hat.com>, netdev@...r.kernel.org,
        "moderated list:INTEL ETHERNET DRIVERS" 
        <intel-wired-lan@...ts.osuosl.org>, mschmidt@...hat.com,
        open list <linux-kernel@...r.kernel.org>, poros@...hat.com,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>, jacob.e.keller@...el.com
Subject: Re: [Intel-wired-lan] [PATCH net] ice: Fix incorrect locking in ice_vc_process_vf_msg()

On Thu, Mar 31, 2022 at 6:17 AM Maciej Fijalkowski
<maciej.fijalkowski@...el.com> wrote:
>
> On Thu, Mar 31, 2022 at 03:14:32PM +0200, Maciej Fijalkowski wrote:
> > On Thu, Mar 31, 2022 at 12:50:04PM +0200, Ivan Vecera wrote:
> > > Usage of mutex_trylock() in ice_vc_process_vf_msg() is incorrect
> > > because message sent from VF is ignored and never processed.
> > >
> > > Use mutex_lock() instead to fix the issue. It is safe because this
> >
> > We need to know what is *the* issue in the first place.
> > Could you please provide more context what is being fixed to the readers
> > that don't have an access to bugzilla?
> >
> > Specifically, what is the case that ignoring a particular message when
> > mutex is already held is a broken behavior?
>
> Uh oh, let's
> CC: Brett Creeley <brett@...sando.io>

My concern here is that we don't want to handle messages
from the context of the "previous" VF configuration if that
makes sense.

It might be best to grab the cfg_lock before doing any
message/VF validating in ice_vc_process_vf_msg() to
make sure all of the checks are done under the cfg_lock.

CC'ing Jake so he can provide some input as
well.

>
> >
> > > mutex is used to prevent races between VF related NDOs and
> > > handlers processing request messages from VF and these handlers
> > > are running in ice_service_task() context.
> > >
> > > Fixes: e6ba5273d4ed ("ice: Fix race conditions between virtchnl handling and VF ndo ops")
> > > Signed-off-by: Ivan Vecera <ivecera@...hat.com>
> > > ---
> > >  drivers/net/ethernet/intel/ice/ice_virtchnl.c | 10 +---------
> > >  1 file changed, 1 insertion(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/intel/ice/ice_virtchnl.c b/drivers/net/ethernet/intel/ice/ice_virtchnl.c
> > > index 3f1a63815bac..9bf5bb008128 100644
> > > --- a/drivers/net/ethernet/intel/ice/ice_virtchnl.c
> > > +++ b/drivers/net/ethernet/intel/ice/ice_virtchnl.c
> > > @@ -3660,15 +3660,7 @@ void ice_vc_process_vf_msg(struct ice_pf *pf, struct ice_rq_event_info *event)
> > >             return;
> > >     }
> > >
> > > -   /* VF is being configured in another context that triggers a VFR, so no
> > > -    * need to process this message
> > > -    */
> > > -   if (!mutex_trylock(&vf->cfg_lock)) {
> > > -           dev_info(dev, "VF %u is being configured in another context that will trigger a VFR, so there is no need to handle this message\n",
> > > -                    vf->vf_id);
> > > -           ice_put_vf(vf);
> > > -           return;
> > > -   }
> > > +   mutex_lock(&vf->cfg_lock);
> > >
> > >     switch (v_opcode) {
> > >     case VIRTCHNL_OP_VERSION:
> > > --
> > > 2.34.1
> > >
> > > _______________________________________________
> > > Intel-wired-lan mailing list
> > > Intel-wired-lan@...osl.org
> > > https://lists.osuosl.org/mailman/listinfo/intel-wired-lan

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