netdev - [PATCH net-next] 802: fix a possible race condition

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Message-Id: <1364975560-6812-1-git-send-email-amwang@redhat.com>
Date:	Wed,  3 Apr 2013 15:52:40 +0800
From:	Cong Wang <amwang@...hat.com>
To:	netdev@...r.kernel.org
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	David Ward <david.ward@...mit.edu>,
	"Jorge Boncompte [DTI2]" <jorge@...2.net>,
	Cong Wang <amwang@...hat.com>
Subject: [PATCH net-next] 802: fix a possible race condition

From: Cong Wang <amwang@...hat.com>

(Resend with a better changelog)

garp_pdu_queue() should ways be called with this spin lock.
garp_uninit_applicant() only holds rtnl lock which is not
enough here.  A possible race can happen as garp_pdu_rcv()
is called in BH context:

	garp_pdu_rcv()
	  |->garp_pdu_parse_msg()
	    |->garp_pdu_parse_attr()
	      |-> garp_gid_event()

Found by code inspection.

Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: David Ward <david.ward@...mit.edu>
Cc: "Jorge Boncompte [DTI2]" <jorge@...2.net>
Signed-off-by: Cong Wang <amwang@...hat.com>
---
 net/802/garp.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/net/802/garp.c b/net/802/garp.c
index 8456f5d..5d9630a 100644
--- a/net/802/garp.c
+++ b/net/802/garp.c
@@ -609,8 +609,12 @@ void garp_uninit_applicant(struct net_device *dev, struct garp_application *appl
 	/* Delete timer and generate a final TRANSMIT_PDU event to flush out
 	 * all pending messages before the applicant is gone. */
 	del_timer_sync(&app->join_timer);
+
+	spin_lock_bh(&app->lock);
 	garp_gid_event(app, GARP_EVENT_TRANSMIT_PDU);
 	garp_pdu_queue(app);
+	spin_unlock_bh(&app->lock);
+
 	garp_queue_xmit(app);
 
 	dev_mc_del(dev, appl->proto.group_address);
-- 
1.7.7.6

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