netdev - Re: [PATCH net 3/3] ipv6: prevent possible UAF in ip6

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Message-ID: <CANn89iL6z0kfsAONLyt7r0_xNbj1xsjdzaB60XTSr1aW7vW+Mw@mail.gmail.com>
Date: Mon, 19 Aug 2024 17:22:45 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: David Ahern <dsahern@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Vasily Averin <vvs@...tuozzo.com>
Subject: Re: [PATCH net 3/3] ipv6: prevent possible UAF in ip6_xmit()

On Mon, Aug 19, 2024 at 5:21 PM David Ahern <dsahern@...nel.org> wrote:
>
> On 8/19/24 7:48 AM, Eric Dumazet wrote:
> > diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> > index 1b9ebee7308f02a626c766de1794e6b114ae8554..519690514b2d1520a311adbcfaa8c6a69b1e85d3 100644
> > --- a/net/ipv6/ip6_output.c
> > +++ b/net/ipv6/ip6_output.c
> > @@ -287,11 +287,15 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
> >               head_room += opt->opt_nflen + opt->opt_flen;
> >
> >       if (unlikely(head_room > skb_headroom(skb))) {
> > +             /* Make sure idev stays alive */
> > +             rcu_read_lock();
> >               skb = skb_expand_head(skb, head_room);
> >               if (!skb) {
> > +                     rcu_read_unlock();
> >                       IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
>
> rcu_read_unlock after INC_STATS

Indeed, thanks for noticing.