netdev - Re: [PATCH net-next] net: dm9051: Fix use after free in dm9051_loop

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Message-ID: <20220221103115.GC3965@kadam>
Date:   Mon, 21 Feb 2022 13:31:15 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Joseph CHAMG <josright123@...il.com>, netdev@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next] net: dm9051: Fix use after free in
 dm9051_loop_tx()

On Fri, Feb 18, 2022 at 09:07:12PM -0800, Jakub Kicinski wrote:
> On Fri, 18 Feb 2022 18:27:30 +0300 Dan Carpenter wrote:
> > This code dereferences "skb" after calling dev_kfree_skb().
> > 
> > Fixes: 2dc95a4d30ed ("net: Add dm9051 driver")
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> Thanks!  Although..
> 
> > diff --git a/drivers/net/ethernet/davicom/dm9051.c b/drivers/net/ethernet/davicom/dm9051.c
> > index a63d17e669a0..f6b5d2becf5e 100644
> > --- a/drivers/net/ethernet/davicom/dm9051.c
> > +++ b/drivers/net/ethernet/davicom/dm9051.c
> > @@ -850,13 +850,13 @@ static int dm9051_loop_tx(struct board_info *db)
> >  		if (skb) {
> >  			ntx++;
> >  			ret = dm9051_single_tx(db, skb->data, skb->len);
> > +			ndev->stats.tx_bytes += skb->len;
> > +			ndev->stats.tx_packets++;
> >  			dev_kfree_skb(skb);
> >  			if (ret < 0) {
> >  				db->bc.tx_err_counter++;
> >  				return 0;
> >  			}
> > -			ndev->stats.tx_bytes += skb->len;
> > -			ndev->stats.tx_packets++;
> 
> I think the idea was (and it often is with this kind of bugs)
> to count only successful transmissions. Could you re-jig it 
> a little to keep those semantics?

Sure.  Will resend.

regards,
dan carpenter