From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Yongjun Subject: Re: [PATCH] SCTP: fix race between sctp_bind_addr_free() and sctp_bind_addr_conflict() Date: Wed, 18 May 2011 17:02:40 +0800 Message-ID: <4DD38B30.9090601@cn.fujitsu.com> References: <1305704885.2983.4.camel@edumazet-laptop> <1305707358.2983.14.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Eric Dumazet , netdev@vger.kernel.org, Vlad Yasevich To: Jacek Luczak Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:63020 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755814Ab1ERJDF convert rfc822-to-8bit (ORCPT ); Wed, 18 May 2011 05:03:05 -0400 In-Reply-To: <1305707358.2983.14.camel@edumazet-laptop> Sender: netdev-owner@vger.kernel.org List-ID: > Le mercredi 18 mai 2011 =C3=A0 10:06 +0200, Jacek Luczak a =C3=A9crit= : >> 2011/5/18 Eric Dumazet : >>> If you're removing items from this list, you must be a writer here,= with >>> exclusive access. So rcu_read_lock()/rcu_read_unlock() is not neces= sary. >> I could agree to some extend ... but strict RCU section IMO is neede= d here. >> I can check this if the issue exists. >> > I can tell you for sure rcu_read_lock() is not needed here. Its only > showing confusion from code's author. > > Please read Documentation/RCU/listRCU.txt for concise explanations, > line 117. > > >>> Therefore, I guess following code is better : >>> >>> list_for_each_entry(addr, &bp->address_list, list) { >>> list_del_rcu(&addr->list); >>> call_rcu(&addr->rcu, sctp_local_addr_free); >>> SCTP_DBG_OBJCNT_DEC(addr); >>> } >>> >>> Then, why dont you fix sctp_bind_addr_clean() instead ? >>> >>> if 'struct sctp_sockaddr_entry' is recu protected, then all frees s= hould >>> be protected as well. >> The _clean() as claimed by Vlad is called many times from various pl= aces >> in code and this could give a overhead. I guess Vlad would need to c= omment. > I guess a full review of this code is needed. You'll have to prove > sctp_bind_addr_clean() is always called after one RCU grace period if > you want to leave it as is. > > You cant get RCU for free, some rules must be followed or you risk > crashes. > fix the race between sctp_bind_addr_free() and sctp_bind_addr_conflict(= ), maybe you just need to remove the socket from the port hash before empty the bind addr= ess list. some thing like this, not test. diff --git a/net/sctp/endpointola.c b/net/sctp/endpointola.c index c8cc24e..924d846 100644 --- a/net/sctp/endpointola.c +++ b/net/sctp/endpointola.c @@ -268,12 +268,13 @@ static void sctp_endpoint_destroy(struct sctp_end= point *ep) =20 /* Cleanup. */ sctp_inq_free(&ep->base.inqueue); - sctp_bind_addr_free(&ep->base.bind_addr); =20 /* Remove and free the port */ if (sctp_sk(ep->base.sk)->bind_hash) sctp_put_port(ep->base.sk); =20 + sctp_bind_addr_free(&ep->base.bind_addr); + /* Give up our hold on the sock. */ if (ep->base.sk) sock_put(ep->base.sk);