From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Ricardo Leitner Subject: Re: [PATCH net-next] sctp: avoid list_del_init if it's freeing the memory right away Date: Wed, 8 Feb 2017 17:57:47 -0200 Message-ID: <20170208195747.GE3414@localhost.localdomain> References: <20170207.142121.1027174926882132252.davem@davemloft.net> <20170207194508.GD3414@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-sctp@vger.kernel.org, vyasevich@gmail.com, nhorman@tuxdriver.com To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43970 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751025AbdBHT6T (ORCPT ); Wed, 8 Feb 2017 14:58:19 -0500 Content-Disposition: inline In-Reply-To: <20170207194508.GD3414@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Feb 07, 2017 at 05:45:09PM -0200, Marcelo Ricardo Leitner wrote: > On Tue, Feb 07, 2017 at 02:21:21PM -0500, David Miller wrote: > > From: Marcelo Ricardo Leitner > > Date: Tue, 7 Feb 2017 17:03:21 -0200 > > > > > There is no reason to use list_del_init() in these places as we are > > > going to free/destroy the memory in a few lines below. > > > > > > Signed-off-by: Marcelo Ricardo Leitner > > > --- > > > net/sctp/associola.c | 14 ++++---------- > > > net/sctp/auth.c | 8 ++------ > > > net/sctp/chunk.c | 4 ++-- > > > net/sctp/outqueue.c | 14 +++++++------- > > > net/sctp/sm_make_chunk.c | 3 +-- > > > 5 files changed, 16 insertions(+), 27 deletions(-) > > > > > > diff --git a/net/sctp/associola.c b/net/sctp/associola.c > > > index e50dc6d7543fd6acfa7442f3a9ee575203c7718d..7eb9dacfa53a438b20a34319cf01c6c9a591f0c3 100644 > > > --- a/net/sctp/associola.c > > > +++ b/net/sctp/associola.c > > > @@ -1638,25 +1638,19 @@ int sctp_assoc_set_id(struct sctp_association *asoc, gfp_t gfp) > > > static void sctp_assoc_free_asconf_queue(struct sctp_association *asoc) > > > { > > > struct sctp_chunk *asconf; > > > - struct sctp_chunk *tmp; > > > > > > - list_for_each_entry_safe(asconf, tmp, &asoc->addip_chunk_list, list) { > > > - list_del_init(&asconf->list); > > > + list_for_each_entry(asconf, &asoc->addip_chunk_list, list) > > > sctp_chunk_free(asconf); > > > - } > > > } > > > > This leave freed memory on the asoc->addip_chunk_list, in fact why aren't you seeing > > This should be alright, because here we are purging the entire list and > the asoc will also be free right after. > > > the BUG_ON() in sctp_chunk_destroy() get triggered? If you elide the list_del() here > > then the "list_empty(&chunk->list)" check there will not be true. > > > > Good question. I have to double check this, but you're probably right. Now I managed to trigger the BUG_ON, as you anticipated. > > > I don't think this transformation here is legal at all. Yeah it's not. It would be relying on freed memory to find the next elements. Uff, sorry. Thanks, Marcelo