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net: skb_free_datagram_locked() fix

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Commit 4b0b72f7dd ( net: speedup udp receive path )
introduced a bug in skb_free_datagram_locked().

We should not skb_orphan() skb if we dont have the guarantee we are the
last skb user, this might happen with MSG_PEEK concurrent users.

To keep socket locked for the smallest period of time, we split
consume_skb() logic, inlined in skb_free_datagram_locked()

Reported-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-05-03 23:18:14 -07:00 committed by David S. Miller
parent f546061840
commit 93bb64eac1
1 changed files with 7 additions and 2 deletions
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9
net/core/datagram.c
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@ -229,13 +229,18 @@ EXPORT_SYMBOL(skb_free_datagram);
void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb) void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
{ {
if (likely(atomic_read(&skb->users) == 1))
smp_rmb();
else if (likely(!atomic_dec_and_test(&skb->users)))
return;
lock_sock_bh(sk); lock_sock_bh(sk);
skb_orphan(skb); skb_orphan(skb);
sk_mem_reclaim_partial(sk); sk_mem_reclaim_partial(sk);
unlock_sock_bh(sk); unlock_sock_bh(sk);
/* skb is now orphaned, might be freed outside of locked section */ /* skb is now orphaned, can be freed outside of locked section */
consume_skb(skb); __kfree_skb(skb);
} }
EXPORT_SYMBOL(skb_free_datagram_locked); EXPORT_SYMBOL(skb_free_datagram_locked);