From 254d900b801fc04aa524ff7bafe28fdd1dbf0ed6 Mon Sep 17 00:00:00 2001 From: Vasily Averin Date: Fri, 14 Jul 2017 12:04:16 +0300 Subject: [PATCH] ipv4: ip_do_fragment: fix headroom tests Some time ago David Woodhouse reported skb_under_panic when we try to push ethernet header to fragmented ipv6 skbs. It was fixed for ipv6 by Florian Westphal in commit 1d325d217c7f ("ipv6: ip6_fragment: fix headroom tests and skb leak") However similar problem still exist in ipv4. It does not trigger skb_under_panic due paranoid check in ip_finish_output2, however according to Alexey Kuznetsov current state is abnormal and ip_fragment should be fixed too. Signed-off-by: Vasily Averin Signed-off-by: David S. Miller --- net/ipv4/ip_output.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 7eb252dcecee..50c74cd890bc 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -599,6 +599,7 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, hlen = iph->ihl * 4; mtu = mtu - hlen; /* Size of data space */ IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE; + ll_rs = LL_RESERVED_SPACE(rt->dst.dev); /* When frag_list is given, use it. First, check its validity: * some transformers could create wrong frag_list or break existing @@ -614,14 +615,15 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, if (first_len - hlen > mtu || ((first_len - hlen) & 7) || ip_is_fragment(iph) || - skb_cloned(skb)) + skb_cloned(skb) || + skb_headroom(skb) < ll_rs) goto slow_path; skb_walk_frags(skb, frag) { /* Correct geometry. */ if (frag->len > mtu || ((frag->len & 7) && frag->next) || - skb_headroom(frag) < hlen) + skb_headroom(frag) < hlen + ll_rs) goto slow_path_clean; /* Partially cloned skb? */ @@ -711,8 +713,6 @@ slow_path: left = skb->len - hlen; /* Space per frame */ ptr = hlen; /* Where to start from */ - ll_rs = LL_RESERVED_SPACE(rt->dst.dev); - /* * Fragment the datagram. */ -- 2.20.1