From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH] igmp: fix ip_mc_sf_allow race Date: Sun, 03 Jan 2010 21:54:41 -0800 (PST) Message-ID: <20100103.215441.43026709.davem@davemloft.net> References: <1262183005-28406-1-git-send-email-fleitner@redhat.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: fleitner@redhat.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:48512 "EHLO sunset.davemloft.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750824Ab0ADFyi (ORCPT ); Mon, 4 Jan 2010 00:54:38 -0500 In-Reply-To: <1262183005-28406-1-git-send-email-fleitner@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Flavio Leitner Date: Wed, 30 Dec 2009 12:23:25 -0200 > Almost all igmp functions accessing inet->mc_list are protected by > rtnl_lock(), but there is one exception which is ip_mc_sf_allow(), > so there is a chance of either ip_mc_drop_socket or ip_mc_leave_group > remove an entry while ip_mc_sf_allow is running causing a crash. > > Signed-off-by: Flavio Leitner Have you triggered this in practice or is this due purely to code inspection? That new synchronize_rcu() is very expensive and will decrease the rate at which groups can be joined and left, _especially_ on high cpu count machines. I do not think it is therefore a suitable problem to this race, if it does in fact exist.