From 93bb64eac10aad3dae6178d7da94765f207d121f Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 3 May 2010 23:18:14 -0700
Subject: [PATCH] net: skb_free_datagram_locked() fix
Commit 4b0b72f7dd617b ( 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>
---
net/core/datagram.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 95b851f3d713..e0097531417a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -229,13 +229,18 @@ EXPORT_SYMBOL(skb_free_datagram);
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);
skb_orphan(skb);
sk_mem_reclaim_partial(sk);
unlock_sock_bh(sk);
- /* skb is now orphaned, might be freed outside of locked section */
- consume_skb(skb);
+ /* skb is now orphaned, can be freed outside of locked section */
+ __kfree_skb(skb);
}
EXPORT_SYMBOL(skb_free_datagram_locked);
--
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