Messages in this thread | | | Subject | Re: [PATCH IPV6 1/1] ipv6: allocate enough headroom in ip6_finish_output2() | From | Eric Dumazet <> | Date | Wed, 7 Jul 2021 19:41:44 +0200 |
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On 7/7/21 6:42 PM, Jakub Kicinski wrote: > On Wed, 7 Jul 2021 08:45:13 -0600 David Ahern wrote: >> On 7/7/21 8:04 AM, Vasily Averin wrote: >>> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c >>> index ff4f9eb..e5af740 100644 >>> --- a/net/ipv6/ip6_output.c >>> +++ b/net/ipv6/ip6_output.c >>> @@ -61,9 +61,24 @@ 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; >>> const struct in6_addr *nexthop; >>> + unsigned int hh_len = LL_RESERVED_SPACE(dev); >>> struct neighbour *neigh; >>> int ret; >>> >>> + /* Be paranoid, rather than too clever. */ >>> + if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) { >>> + struct sk_buff *skb2; >>> + >>> + skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev)); >> >> why not use hh_len here? > > Is there a reason for the new skb? Why not pskb_expand_head()?
pskb_expand_head() might crash, if skb is shared.
We possibly can add a helper, factorizing all this, and eventually use pskb_expand_head() if safe.
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