Re: [PATCH net-next] cxgb4: fix memory leak in cxgb4_init_ethtool_filters() error path

[Simon Horman <horms@kernel.org>]

On Fri, Apr 11, 2025 at 09:52:29PM +0530, Abdun Nihaal wrote:
> On Fri, Apr 11, 2025 at 03:57:34PM +0100, Simon Horman wrote:
> > On Wed, Apr 09, 2025 at 05:47:46PM +0200, Markus Elfring wrote:
> > > …
> > > > +++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_ethtool.c
> > > > @@ -2270,6 +2270,7 @@ int cxgb4_init_ethtool_filters(struct adapter *adap)
> > > >  		eth_filter->port[i].bmap = bitmap_zalloc(nentries, GFP_KERNEL);
> > > >  		if (!eth_filter->port[i].bmap) {
> > > >  			ret = -ENOMEM;
> > > > +			kvfree(eth_filter->port[i].loc_array);
> > > >  			goto free_eth_finfo;
> > > >  		}
> > > >  	}
> > > 
> > > How do you think about to move the shown error code assignment behind the mentioned label
> > > (so that another bit of duplicate source code could be avoided)?
> > 
> > Hi Markus,
> > 
> > If you mean something like the following. Then I agree that it
> > is both in keeping with the existing error handling in this function
> > and addresses the problem at hand.
> > 
> > diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_ethtool.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_ethtool.c
> > index 7f3f5afa864f..df26d3388c00 100644
> > --- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_ethtool.c
> > +++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_ethtool.c
> > @@ -2270,13 +2270,15 @@ int cxgb4_init_ethtool_filters(struct adapter *adap)
> >                 eth_filter->port[i].bmap = bitmap_zalloc(nentries, GFP_KERNEL);
> >                 if (!eth_filter->port[i].bmap) {
> >                         ret = -ENOMEM;
> > -                       goto free_eth_finfo;
> > +                       goto free_eth_finfo_loc_array;
> >                 }
> >         }
> > 
> >         adap->ethtool_filters = eth_filter;
> >         return 0;
> > 
> > +free_eth_finfo_loc_array:
> > +       kvfree(eth_filter->port[i].loc_array);
> >  free_eth_finfo:
> >         while (i-- > 0) {
> >                 bitmap_free(eth_filter->port[i].bmap);
> > 
> 
> I think what Markus meant, was to move the ret = -ENOMEM from both the
> allocations in the loop, to after the free_eth_finfo label because it is
> -ENOMEM on both goto jumps.
> 
> But personally I would prefer having the ret code right after the call 
> that is failing. Also I would avoid creating new goto labels unless
> necessary, because it is easier to see the kvfree in context inside the
> loop, than to put it in a separate label.
> 
> I just tried to make the most minimal code change to fix the memory leak.

Thanks Nihaal,

I agree that your patch is fine as-is for the reasons you describe above.

Reviewed-by: Simon Horman <horms@kernel.org>