From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [RFC] [PATCH] ipv6: Fix potential hang in mif6_add Date: Wed, 02 May 2012 09:02:40 +0200 Message-ID: <1335942160.22133.51.camel@edumazet-glaptop> References: <20120502060957.30368.34595.sendpatchset@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org To: Krishna Kumar Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:52086 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751185Ab2EBHCp (ORCPT ); Wed, 2 May 2012 03:02:45 -0400 Received: by bkcji2 with SMTP id ji2so166124bkc.19 for ; Wed, 02 May 2012 00:02:44 -0700 (PDT) In-Reply-To: <20120502060957.30368.34595.sendpatchset@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2012-05-02 at 11:39 +0530, Krishna Kumar wrote: > Fix a potential "waiting for %s to become free" hang. > mif6_add() called ip6mr_reg_vif to allocate/register a > netdevice, which also took an extra reference on the > device. On error, mif6_add should drop this reference > before unregistering the device. > > (untested, noticed from code walkthrough) > > Signed-off-by: Krishna Kumar > --- > net/ipv6/ip6mr.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff -ruNp org/net/ipv6/ip6mr.c new/net/ipv6/ip6mr.c > --- org/net/ipv6/ip6mr.c 2012-04-19 09:03:34.000000000 +0530 > +++ new/net/ipv6/ip6mr.c 2012-05-02 10:51:01.953110994 +0530 > @@ -937,8 +937,8 @@ static int mif6_add(struct net *net, str > return -ENOBUFS; > err = dev_set_allmulti(dev, 1); > if (err) { > - unregister_netdevice(dev); > dev_put(dev); > + unregister_netdevice(dev); > return err; > } > break; > This makes no difference to dev_put() before or after unregister_netdevice() because we hold RTNL in mif6_add()