Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753215Ab2JHGXt (ORCPT ); Mon, 8 Oct 2012 02:23:49 -0400 Received: from shrek-modem1.podlesie.net ([83.18.25.171]:56669 "EHLO shrek.podlesie.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751891Ab2JHGXr (ORCPT ); Mon, 8 Oct 2012 02:23:47 -0400 Date: Mon, 8 Oct 2012 08:23:43 +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: <20121008062343.GA28685@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: 3243 Lines: 93 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. > > > vcc = ATM_SKB(skb)->vcc; > + bh_lock_sock(sk_atm(vcc)); After bh_lock_sock() sock_owned_by_user(sk_atm(vcc)) should be checked here. I'm sending fixed patch. > if (test_bit(ATM_VF_RELEASED, &vcc->flags) > || test_bit(ATM_VF_CLOSE, &vcc->flags) Krzysiek -- >From 3ae93335423ed0ba526dc80163ff6dfeba9bbea1 Mon Sep 17 00:00:00 2001 From: Krzysztof Mazur Date: Mon, 8 Oct 2012 08:10:22 +0200 Subject: [PATCH] pppoatm: fix race condition with destroying of vcc The pppoatm_send() calls vcc->send() and now also checks for some vcc flags that indicate destroyed vcc without proper locking. The vcc_sendmsg() uses lock_sock(sk). This lock is used by vcc_release(), so vcc_destroy_socket() will not be called between check and during ->send(). The vcc_release_async() sets ATM_VF_CLOSE, but it should be safe to call ->send() after it, because vcc->dev->ops->close() is not called. The pppoatm_send() is called with BH disabled, so bh_lock_sock() should be used instead of lock_sock(). Signed-off-by: Krzysztof Mazur --- net/atm/pppoatm.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c index 0dcb5dc..e3b2d69 100644 --- a/net/atm/pppoatm.c +++ b/net/atm/pppoatm.c @@ -270,6 +270,7 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) { struct pppoatm_vcc *pvcc = chan_to_pvcc(chan); struct atm_vcc *vcc; + int ret; ATM_SKB(skb)->vcc = pvcc->atmvcc; pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc); @@ -304,17 +305,24 @@ static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb) } vcc = ATM_SKB(skb)->vcc; + bh_lock_sock(sk_atm(vcc)); + if (sock_owned_by_user(sk_atm(vcc))) + goto nospace_unlock_sock; if (test_bit(ATM_VF_RELEASED, &vcc->flags) || test_bit(ATM_VF_CLOSE, &vcc->flags) || !test_bit(ATM_VF_READY, &vcc->flags)) - goto nospace; + goto nospace_unlock_sock; atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc); ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options; pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev); - return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) + ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) ? DROP_PACKET : 1; + bh_unlock_sock(sk_atm(vcc)); + return ret; +nospace_unlock_sock: + bh_unlock_sock(sk_atm(vcc)); nospace: /* * We don't have space to send this SKB now, but we might have -- 1.7.12.2.2.g1c3c581 -- 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/