| From | Ben Hutchings <> | Date | Sat, 09 Sep 2017 22:47:14 +0100 | Subject | [PATCH 3.16 009/233] netem: fix skb_orphan_partial() |
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3.16.48-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
commit f6ba8d33cfbb46df569972e64dbb5bb7e929bfd9 upstream.
I should have known that lowering skb->truesize was dangerous :/
In case packets are not leaving the host via a standard Ethernet device, but looped back to local sockets, bad things can happen, as reported by Michael Madsen ( https://bugzilla.kernel.org/show_bug.cgi?id=195713 )
So instead of tweaking skb->truesize, lets change skb->destructor and keep a reference on the owner socket via its sk_refcnt.
Fixes: f2f872f9272a ("netem: Introduce skb_orphan_partial() helper") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Michael Madsen <mkm@nabto.com> Signed-off-by: David S. Miller <davem@davemloft.net> [bwh: Backported to 3.16: drop changes to the preceding comment and the fast path, which we don't have] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1654,17 +1654,17 @@ EXPORT_SYMBOL(sock_wfree); void skb_orphan_partial(struct sk_buff *skb) { - /* TCP stack sets skb->ooo_okay based on sk_wmem_alloc, - * so we do not completely orphan skb, but transfert all - * accounted bytes but one, to avoid unexpected reorders. - */ if (skb->destructor == sock_wfree #ifdef CONFIG_INET || skb->destructor == tcp_wfree #endif ) { - atomic_sub(skb->truesize - 1, &skb->sk->sk_wmem_alloc); - skb->truesize = 1; + struct sock *sk = skb->sk; + + if (atomic_inc_not_zero(&sk->sk_refcnt)) { + atomic_sub(skb->truesize, &sk->sk_wmem_alloc); + skb->destructor = sock_efree; + } } else { skb_orphan(skb); }
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