gro: Re-fix different skb headrooms

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 : https://bugzilla.kernel.org/show_bug.cgi?id=16626
fixes commit: 3d3be4333fdf6faa080947b331a6a19bce1a4f57

Reported-by: Plamen Petrov <pvp-lsts@fs.uni-ruse.bg>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Plamen Petrov <pvp-lsts@fs.uni-ruse.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c1c86f5fe05aa52821e02d0aa53401577265974e..9e7214e2b46a1ae739eacf2b5d9092ce3cc529d9 100644 (file)
--- 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;