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Subject[34-longterm 111/260] gro: Re-fix different skb headrooms
From: Jarek Poplawski <>

commit 64289c8e6851bca0e589e064c9a5c9fbd6ae5dd4 upstream.

The patch: "gro: fix different skb headrooms" in its part:
"2) allocate a minimal skb for head of frag_list" is buggy. The copied
skb has p->data set at the ip header at the moment, and skb_gro_offset
is the length of ip + tcp headers. So, after the change the length of
mac header is skipped. Later skb_set_mac_header() sets it into the
NET_SKB_PAD area (if it's long enough) and ip header is misaligned at
NET_SKB_PAD + NET_IP_ALIGN offset. There is no reason to assume the
original skb was wrongly allocated, so let's copy it as it was.

bugzilla :
fixes commit: 3d3be4333fdf6faa080947b331a6a19bce1a4f57

Reported-by: Plamen Petrov <>
Signed-off-by: Jarek Poplawski <>
CC: Eric Dumazet <>
Acked-by: Eric Dumazet <>
Tested-by: Plamen Petrov <>
Signed-off-by: David S. Miller <>
Signed-off-by: Paul Gortmaker <>
net/core/skbuff.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c1c86f5..9e7214e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2711,7 +2711,7 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
} else if (skb_gro_len(p) != pinfo->gso_size)
return -E2BIG;

- headroom = NET_SKB_PAD + NET_IP_ALIGN;
+ headroom = skb_headroom(p);
nskb = alloc_skb(headroom + skb_gro_offset(p), GFP_ATOMIC);
if (unlikely(!nskb))
return -ENOMEM;

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