Re: [PATCH net-next] netlink: Fix potential skb memleak in netlink_ack

[Tao Chen]

在 2022/11/3 上午5:39, Jakub Kicinski 写道:
> On Wed,  2 Nov 2022 20:08:20 +0800 Tao Chen wrote:
> > We should clean the skb resource if nlmsg_put/append failed
> > , so fix it.
>
> The comma should be at the end of the previous line.
> But really the entire ", so fix it." is redundant.
Thank you, i will pay attention next time
> > Fiexs: commit 738136a0e375 ("netlink: split up copies in the
> > ack construction")
>
> Please look around to see how to correctly format a Fixes tag
> (including not line wrapping it).
>
> How did you find this bug? An automated tool? Syzbot?
>
> One more note below on the code itself.
This was found by the coverity tool, i will add it.
> > Signed-off-by: Tao Chen <chentao.kernel@xxxxxxxxxxxxxxxxx>
> > ---
> >   net/netlink/af_netlink.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> > index c6b8207e..9d73dae 100644
> > --- a/net/netlink/af_netlink.c
> > +++ b/net/netlink/af_netlink.c
> > @@ -2500,7 +2500,7 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
> >   
> >   	skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
> >   	if (!skb)
> > -		goto err_bad_put;
> > +		goto err_skb;
> >   
> >   	rep = nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
> >   			NLMSG_ERROR, sizeof(*errmsg), flags);
> > @@ -2528,6 +2528,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
> >   	return;
> >   
> >   err_bad_put:
> > +	kfree_skb(skb);
>
> Please use nlmsg_free() since we allocated with nlmsg_new().
Ok, i will send it in v2.
> > +err_skb:
> >   	NETLINK_CB(in_skb).sk->sk_err = ENOBUFS;
> >   	sk_error_report(NETLINK_CB(in_skb).sk);
> >   }