Subject: Re: [PATCH net] net: stmmac: selftests: fix potential memleak in stmmac_test_arpoffload()

From: Leon Romanovsky <[email-masked]>
Date: Thu, 8 Dec 2022 10:29:06 +0200

On Wed, Dec 07, 2022 at 06:07:16PM +0800, Zhang Changzhong wrote:
> On 2022/12/7 17:12, Leon Romanovsky wrote:
> > On Wed, Dec 07, 2022 at 04:31:59PM +0800, Zhang Changzhong wrote:
> >> The skb allocated by stmmac_test_get_arp_skb() hasn't been released in
> >> some error handling case, which will lead to a memory leak. Fix this up
> >> by adding kfree_skb() to release skb.
> >>
> >> Compile tested only.
> >>
> >> Fixes: 5e3fb0a6e2b3 ("net: stmmac: selftests: Implement the ARP Offload test")
> >> Signed-off-by: Zhang Changzhong <[email-masked]>
> >> ---
> >>  drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c | 8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
> >> index 49af7e7..687f43c 100644
> >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
> >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
> >> @@ -1654,12 +1654,16 @@ static int stmmac_test_arpoffload(struct stmmac_priv *priv)
> >>  	}
> >>  
> >>  	ret = stmmac_set_arp_offload(priv, priv->hw, true, ip_addr);
> >> -	if (ret)
> >> +	if (ret) {
> >> +		kfree_skb(skb);
> >>  		goto cleanup;
> >> +	}
> >>  
> >>  	ret = dev_set_promiscuity(priv->dev, 1);
> >> -	if (ret)
> >> +	if (ret) {
> >> +		kfree_skb(skb);
> >>  		goto cleanup;
> >> +	}
> >>  
> >>  	ret = dev_direct_xmit(skb, 0);
> >>  	if (ret)
> > 
> > You should release skb here too. So the better patch will be to write
> > something like that:
> > 
> 
> Hi Leon,
> 
> Thanks for your review, but I don't think we need release skb here,
> because dev_direct_xmit() is responsible for freeing it.

Interesting, __dev_direct_xmit() releases skb too.
Thanks for the clarification.

> 
> Regards,
> Changzhong
> 
> > cleanup:
> >   stmmac_set_arp_offload(priv, priv->hw, false, 0x0);
> >   if (ret)
> >   	kfree_skb(skb);
> >> Thanks
> > 
> >> -- 
> >> 2.9.5
> >>
> > .
> >