Commit 113ab386 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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->

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

skb_reserve(skb, LL_RESERVED_SPACE(rt->;

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: default avatarElmar Vonlanthen <>
Signed-off-by: default avatarEric Dumazet <>
CC: Timo Teräs <>
CC: Herbert Xu <>
Signed-off-by: default avatarDavid S. Miller <>
parent fd11e153
......@@ -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) {
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