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netem: fix skb_orphan_partial()

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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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2017-05-11 15:24:41 -07:00 committed by Greg Kroah-Hartman
parent 338f665acb
commit 605b6b2b4d
1 changed files with 6 additions and 6 deletions
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12
net/core/sock.c
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@ -1690,17 +1690,17 @@ EXPORT_SYMBOL(skb_set_owner_w);
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);
}