Commit 113ab386 authored Oct 14, 2011 by Eric Dumazet Committed by David S. Miller Oct 20, 2011

ip_gre: dont increase dev->needed_headroom on a live device



It seems ip_gre is able to change dev->needed_headroom on the fly.

Its is not legal unfortunately and triggers a BUG in raw_sendmsg()

skb = sock_alloc_send_skb(sk, ... + LL_ALLOCATED_SPACE(rt->dst.dev)

< another cpu change dev->needed_headromm (making it bigger)

...
skb_reserve(skb, LL_RESERVED_SPACE(rt->dst.dev));

We end with LL_RESERVED_SPACE() being bigger than LL_ALLOCATED_SPACE()
-> we crash later because skb head is exhausted.

Bug introduced in commit 243aad83 in 2.6.34 (ip_gre: include route
header_len in max_headroom calculation)

Reported-by: Elmar Vonlanthen <evonlanthen@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Timo Teräs <timo.teras@iki.fi>
CC: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent fd11e153

net/ipv4/ip_gre.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -835,8 +835,6 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff skb, struct net_device dev
		if (skb_headroom(skb) < max_headroom \|\| skb_shared(skb)\|\|
		(skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
		if (max_headroom > dev->needed_headroom)
		dev->needed_headroom = max_headroom;
		if (!new_skb) {
		ip_rt_put(rt);
		dev->stats.tx_dropped++;

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