Messages in this thread | | | Subject | Re: [PATCH IPV6 v3 1/1] ipv6: allocate enough headroom in ip6_finish_output2() | From | Vasily Averin <> | Date | Tue, 13 Jul 2021 10:46:14 +0300 |
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I've found 2 problems in this patch, and I'm going to resend new patch version soon.
On 7/12/21 9:45 AM, Vasily Averin wrote: > index ff4f9eb..0efcb9b 100644 > --- a/net/ipv6/ip6_output.c > +++ b/net/ipv6/ip6_output.c > @@ -60,10 +60,38 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff * > { > struct dst_entry *dst = skb_dst(skb); > struct net_device *dev = dst->dev; > + unsigned int hh_len = LL_RESERVED_SPACE(dev); > + int delta = hh_len - skb_headroom(skb); > const struct in6_addr *nexthop; > struct neighbour *neigh; > int ret; > > + /* Be paranoid, rather than too clever. */ > + if (unlikely(delta > 0) && dev->header_ops) { > + /* pskb_expand_head() might crash, if skb is shared */ > + if (skb_shared(skb)) { > + struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC); > + > + if (likely(nskb)) { > + if (skb->sk) > + skb_set_owner_w(skb, skb->sk);
need to assign sk not to skb but to nskb
> + consume_skb(skb); > + } else { > + kfree_skb(skb);
It is quite strange to call consume_skb() on one case and kfree_skb() in another one. We know that original skb was shared so we should not call kfree_skb here.
Btw I've noticed similar problem in few other cases: in pptp_xmit, pvc_xmit, ip_vs_prepare_tunneled_skb they call consume_skb() in case of success and kfree_skb on error path. It looks like potential bug for me.
> + } > + skb = nskb; > + } > + if (skb && > + pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) { > + kfree_skb(skb); > + skb = NULL; > + } > + if (!skb) { > + IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTDISCARDS); > + return -ENOMEM; > + } > + } > + > if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) { > struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb)); > >
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