Subject: Re: [PATCH net] nfp: flower: avoid taking mutex in atomic context

From: Simon Horman <[email-masked]>
Date: Tue, 31 Jan 2023 13:15:46 +0100

On Tue, Jan 31, 2023 at 01:45:10PM +0200, Leon Romanovsky wrote:
> On Tue, Jan 31, 2023 at 09:03:13AM +0100, Simon Horman wrote:
> > From: Yanguo Li <[email-masked]>
> > 
> > A mutex may sleep, which is not permitted in atomic context.
> > Avoid a case where this may arise by moving the to
> > nfp_flower_lag_get_info_from_netdev() in nfp_tun_write_neigh() spinlock.
> > 
> > Fixes: abc210952af7 ("nfp: flower: tunnel neigh support bond offload")
> > Reported-by: Dan Carpenter <[email-masked]>
> > Signed-off-by: Yanguo Li <[email-masked]>
> > Signed-off-by: Simon Horman <[email-masked]>
> > ---
> >  drivers/net/ethernet/netronome/nfp/flower/tunnel_conf.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/netronome/nfp/flower/tunnel_conf.c b/drivers/net/ethernet/netronome/nfp/flower/tunnel_conf.c
> > index a8678d5612ee..060a77f2265d 100644
> > --- a/drivers/net/ethernet/netronome/nfp/flower/tunnel_conf.c
> > +++ b/drivers/net/ethernet/netronome/nfp/flower/tunnel_conf.c
> > @@ -460,6 +460,7 @@ nfp_tun_write_neigh(struct net_device *netdev, struct nfp_app *app,
> >  			    sizeof(struct nfp_tun_neigh_v4);
> >  	unsigned long cookie = (unsigned long)neigh;
> >  	struct nfp_flower_priv *priv = app->priv;
> > +	struct nfp_tun_neigh_lag lag_info;
> >  	struct nfp_neigh_entry *nn_entry;
> >  	u32 port_id;
> >  	u8 mtype;
> > @@ -468,6 +469,11 @@ nfp_tun_write_neigh(struct net_device *netdev, struct nfp_app *app,
> >  	if (!port_id)
> >  		return;
> >  
> > +	if ((port_id & NFP_FL_LAG_OUT) == NFP_FL_LAG_OUT) {
> > +		memset(&lag_info, 0, sizeof(struct nfp_tun_neigh_lag));
> 
> This memset can be removed if you initialize lag_info to zero.
> struct nfp_tun_neigh_lag lag_info = {};

Happy to change if that is preferred.
Is it preferred?

> Thanks
> 
> > +		nfp_flower_lag_get_info_from_netdev(app, netdev, &lag_info);
> > +	}
> > +
> >  	spin_lock_bh(&priv->predt_lock);
> >  	nn_entry = rhashtable_lookup_fast(&priv->neigh_table, &cookie,
> >  					  neigh_table_params);
> > @@ -515,7 +521,7 @@ nfp_tun_write_neigh(struct net_device *netdev, struct nfp_app *app,
> >  		neigh_ha_snapshot(common->dst_addr, neigh, netdev);
> >  
> >  		if ((port_id & NFP_FL_LAG_OUT) == NFP_FL_LAG_OUT)
> > -			nfp_flower_lag_get_info_from_netdev(app, netdev, lag);
> > +			memcpy(lag, &lag_info, sizeof(struct nfp_tun_neigh_lag));
> >  		common->port_id = cpu_to_be32(port_id);
> >  
> >  		if (rhashtable_insert_fast(&priv->neigh_table,
> > -- 
> > 2.30.2
> >