From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Subject: Re: [PATCH] sctp: fix ASCONF list handling Date: Thu, 28 May 2015 10:27:32 -0300 Message-ID: <20150528132732.GC3387@localhost.localdomain> References: <20150528101511.GA14938@hmsreliant.think-freely.org> <20150528111727.GB3387@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-sctp@vger.kernel.org, Daniel Borkmann , Vlad Yasevich , Michio Honda To: Neil Horman Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59138 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751529AbbE1N1f (ORCPT ); Thu, 28 May 2015 09:27:35 -0400 Content-Disposition: inline In-Reply-To: <20150528111727.GB3387@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, May 28, 2015 at 08:17:27AM -0300, Marcelo Ricardo Leitner wrote: > On Thu, May 28, 2015 at 06:15:11AM -0400, Neil Horman wrote: > > On Wed, May 27, 2015 at 09:52:17PM -0300, mleitner@redhat.com wrote: > > > From: Marcelo Ricardo Leitner > > > > > > ->auto_asconf_splist is per namespace and mangled by functions like > > > sctp_setsockopt_auto_asconf() which doesn't guarantee any serialization. > > > > > > Also, the call to inet_sk_copy_descendant() was backuping > > > ->auto_asconf_list through the copy but was not honoring > > > ->do_auto_asconf, which could lead to list corruption if it was > > > different between both sockets. > > > > > > This commit thus fixes the list handling by adding a spinlock to protect > > > against multiple writers and converts the list to be protected by RCU > > > too, so that we don't have a lock inverstion issue at > > > sctp_addr_wq_timeout_handler(). > > > > > > And as this list now uses RCU, we cannot do such backup and restore > > > while copying descendant data anymore as readers may be traversing the > > > list meanwhile. We fix this by simply ignoring/not copying those fields, > > > placed at the end of struct sctp_sock, so we can just ignore it together > > > with struct ipv6_pinfo data. For that we create sctp_copy_descendant() > > > so we don't clutter inet_sk_copy_descendant() with SCTP info. > > > > > > Issue was found with a test application that kept flipping sysctl > > > default_auto_asconf on and off. > > > > > > Fixes: 9f7d653b67ae ("sctp: Add Auto-ASCONF support (core).") > > > Signed-off-by: Marcelo Ricardo Leitner > > > --- > > > include/net/netns/sctp.h | 6 +++++- > > > include/net/sctp/structs.h | 2 ++ > > > net/sctp/protocol.c | 6 +++++- > > > net/sctp/socket.c | 39 ++++++++++++++++++++++++++------------- > > > 4 files changed, 38 insertions(+), 15 deletions(-) > > > > > > diff --git a/include/net/netns/sctp.h b/include/net/netns/sctp.h > > > index 3573a81815ad9e0efb6ceb721eb066d3726419f0..e080bebb3147af39c8275261f57018eb01e917b0 100644 > > > --- a/include/net/netns/sctp.h > > > +++ b/include/net/netns/sctp.h > > > @@ -30,12 +30,15 @@ struct netns_sctp { > > > struct list_head local_addr_list; > > > struct list_head addr_waitq; > > > struct timer_list addr_wq_timer; > > > - struct list_head auto_asconf_splist; > > > + struct list_head __rcu auto_asconf_splist; > > You should use the addr_wq_lock here instead of creating a new lock, as thats > > already used to protect most accesses to the list you are concerned about. > > Ok, that works too. > > > Though truthfully, that shouldn't be necessecary. The list in question is only > > read in one location and only written in one location. You can likely just > > rcu-ify, as the write side is in process context and protected by lock_sock. > > It should, it's not protected by lock_sock as this list resides in > netns_sctp structure, which lock_sock doesn't cover. Write side is in > process context yes, but this list is written in sctp_init_sock(), > sctp_destroy_sock() and sctp_setsockopt_auto_asconf(), so one could > trigger this by either creating/destroying sockets if > default_auto_asconf=1 or just by creating a bunch of sockets and > flipping asconf via setsockopt (or a combination of these operations). > (I'll point this out in the changelog) Hmm.. by reusing addr_wq_lock we don't need to rcu-ify the list, as the reader is inside that lock too, so I can just protect auto_asconf_splist writers with addr_wq_lock. Nice, thanks Neil. Marcelo