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 <v...@virtuozzo.com>
---
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 7eb252d..50c74cd 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 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct
sk_buff *skb,
left = skb->len - hlen; /* Space per frame */
ptr = hlen; /* Where to start from */
- ll_rs = LL_RESERVED_SPACE(rt->dst.dev);
-
/*
* Fragment the datagram.
*/
--
2.7.4
