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Message-Id: <1437008972-9140-5-git-send-email-kamal@canonical.com>
Date: Wed, 15 Jul 2015 18:05:25 -0700
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Eric Dumazet <edumazet@...gle.com>,
Willem de Bruijn <willemb@...gle.com>,
"David S. Miller" <davem@...emloft.net>,
Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 004/251] packet: read num_members once in packet_rcv_fanout()
3.19.8-ckt4 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@...gle.com>
[ Upstream commit f98f4514d07871da7a113dd9e3e330743fd70ae4 ]
We need to tell compiler it must not read f->num_members multiple
times. Otherwise testing if num is not zero is flaky, and we could
attempt an invalid divide by 0 in fanout_demux_cpu()
Note bug was present in packet_rcv_fanout_hash() and
packet_rcv_fanout_lb() but final 3.1 had a simple location
after commit 95ec3eb417115fb ("packet: Add 'cpu' fanout policy.")
Fixes: dc99f600698dc ("packet: Add fanout support.")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
net/packet/af_packet.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9cfe2e1..8c7eb97 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1339,7 +1339,7 @@ static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
struct packet_fanout *f = pt->af_packet_priv;
- unsigned int num = f->num_members;
+ unsigned int num = READ_ONCE(f->num_members);
struct packet_sock *po;
unsigned int idx;
--
1.9.1
--
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