From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: suspicious RCU usage (netlink/rhashtable) Date: Tue, 22 Dec 2015 16:54:00 -0500 Message-ID: <20151222215400.GA14148@codemonkey.org.uk> References: <20151222.164225.926367017579760543.davem@davemloft.net> <20151222214734.GB13231@codemonkey.org.uk> <20151222.165020.297576414018581950.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kraigatgoog@gmail.com, netdev@vger.kernel.org, herbert@gondor.apana.org.au To: David Miller Return-path: Received: from arcturus.aphlor.org ([188.246.204.175]:58886 "EHLO arcturus.aphlor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932680AbbLVVyE (ORCPT ); Tue, 22 Dec 2015 16:54:04 -0500 Content-Disposition: inline In-Reply-To: <20151222.165020.297576414018581950.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Dec 22, 2015 at 04:50:20PM -0500, David Miller wrote: > > > > Simple fix is below. Though, I don't understand the history of the > > > > multiple locks in this structure to be sure it's correct. I'll send > > > > it as a formal patch. Please reject if it's not the right approach. > > > > > > > > diff --git a/lib/rhashtable.c b/lib/rhashtable.c > > > > index 1c149e9..cc80870 100644 > > > > --- a/lib/rhashtable.c > > > > +++ b/lib/rhashtable.c > > > > @@ -516,7 +516,8 @@ int rhashtable_walk_init(struct rhashtable *ht, > > > > struct rhashtable_iter *iter) > > > > return -ENOMEM; > > > > > > > > spin_lock(&ht->lock); > > > > - iter->walker->tbl = rht_dereference(ht->tbl, ht); > > > > + iter->walker->tbl = > > > > + rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock)); > > > > list_add(&iter->walker->list, &iter->walker->tbl->walkers); > > > > spin_unlock(&ht->lock); > > > > > > How can this be the "fix"? That's exactly what's in the tree. > > > > I should have made clear, this is Linus' tree I'm hitting this on, > > which matches what Craig posted. > > Ok, so this should be fixed in my 'net' tree and I'll send that to Linus > soon. Great, thanks Dave. Sorry for the fire-alarm :) Dave