ip_fragment: also adjust skb->truesize for packets not owned by a socket

When a large packet gets reassembled by ip_defrag(), the head skb
accounts for all the fragments in skb->truesize. If this packet is
refragmented again, skb->truesize is not re-adjusted to reflect only
the head size since its not owned by a socket. If the head fragment
then gets recycled and reused for another received fragment, it might
exceed the defragmentation limits due to its large truesize value.

skb_recycle_check() explicitly checks for linear skbs, so any recycled
skb should reflect its true size in skb->truesize. Change ip_fragment()
to also adjust the truesize value of skbs not owned by a socket.

Reported-and-tested-by: Ben Menchaca <ben@bigfootnetworks.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index f989518..4d50daa 100644 (file)
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -501,8 +501,8 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
                        if (skb->sk) {
                                frag->sk = skb->sk;
                                frag->destructor = sock_wfree;
-                               truesizes += frag->truesize;
                        }
+                       truesizes += frag->truesize;
                }
 
                /* Everything is OK. Generate! */