Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754942Ab2JFPqK (ORCPT ); Sat, 6 Oct 2012 11:46:10 -0400 Received: from shrek-modem1.podlesie.net ([83.18.25.171]:39551 "EHLO shrek.podlesie.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754096Ab2JFPqH (ORCPT ); Sat, 6 Oct 2012 11:46:07 -0400 Date: Sat, 6 Oct 2012 17:46:06 +0200 From: Krzysztof Mazur To: David Woodhouse Cc: mitch@sfgoth.com, netdev@vger.kernel.org, davem@davemloft.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] pppoatm: don't send frames to destroyed vcc Message-ID: <20121006154606.GA25588@shrek.podlesie.net> References: <1349525991-21462-1-git-send-email-krzysiek@podlesie.net> <1349530370.6524.2.camel@shinybook.infradead.org> <20121006153804.GA13564@shrek.podlesie.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121006153804.GA13564@shrek.podlesie.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1986 Lines: 56 On Sat, Oct 06, 2012 at 05:38:04PM +0200, Krzysztof Mazur wrote: > On Sat, Oct 06, 2012 at 02:32:50PM +0100, David Woodhouse wrote: > > On Sat, 2012-10-06 at 14:19 +0200, Krzysztof Mazur wrote: > > > Now pppoatm_send(), like vcc_sendmsg(), checks for vcc flags that > > > indicate that vcc is not ready. > > > > And what locking prevents the flag from being set immediately after we > > check it? > > > > nothing, this patch should fix this. > I think there is another problem here. The pppoatm gets a reference to atmvcc, but I don't see anything that protects against removal of that vcc. The vcc uses vcc->sk socket for reference counting, so sock_hold() and sock_put() should be used by pppoatm. diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c index 29afc68..126f57f 100644 --- a/net/atm/pppoatm.c +++ b/net/atm/pppoatm.c @@ -154,6 +154,7 @@ static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc) tasklet_kill(&pvcc->wakeup_tasklet); ppp_unregister_channel(&pvcc->chan); atmvcc->user_back = NULL; + sock_put(sk_atm(pvcc->atmvcc)); kfree(pvcc); /* Gee, I hope we have the big kernel lock here... */ module_put(THIS_MODULE); @@ -371,6 +372,7 @@ static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) if (pvcc == NULL) return -ENOMEM; pvcc->atmvcc = atmvcc; + sock_hold(sk_atm(atmvcc)); /* Maximum is zero, so that we can use atomic_inc_not_zero() */ atomic_set(&pvcc->inflight, NONE_INFLIGHT); @@ -385,6 +387,7 @@ static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan; err = ppp_register_channel(&pvcc->chan); if (err != 0) { + sock_put(sk_atm(atmvcc)); kfree(pvcc); return err; } -- Krzysiek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/