From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [Patch net] garp: fix a NULL pointer dereference bug Date: Mon, 4 Mar 2013 11:36:57 +0800 Message-ID: <1362368217-30984-1-git-send-email-amwang@redhat.com> Cc: bugs@syam.in, David Ward , Stephen Hemminger , "David S. Miller" , Cong Wang To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:32567 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755151Ab3CDDhX (ORCPT ); Sun, 3 Mar 2013 22:37:23 -0500 Sender: netdev-owner@vger.kernel.org List-ID: From: Cong Wang A NULL-deref bug was reported in: https://bugzilla.kernel.org/show_bug.cgi?id=54281 when deleting a vlan interface: # ip link del em1.57 BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] garp_uninit_applicant+0x2f/0xd0 [garp] ... This is probably app->pdu is NULL'ed in garp_pdu_rcv() in BH, while garp_uninit_applicant() only holds rtnl lock which is not enough to prevent this. OTOH, garp_pdu_queue() should ways be called with the spin lock. Reported-by: bugs@syam.in Cc: bugs@syam.in Cc: David Ward Cc: Stephen Hemminger Cc: David S. Miller Signed-off-by: Cong Wang --- 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);