Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757367Ab2J3Jh5 (ORCPT ); Tue, 30 Oct 2012 05:37:57 -0400 Received: from merlin.infradead.org ([205.233.59.134]:42392 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756380Ab2J3Jhz (ORCPT ); Tue, 30 Oct 2012 05:37:55 -0400 Message-ID: <1351589868.17077.34.camel@shinybook.infradead.org> Subject: Re: [PATCH v2 2/3] pppoatm: fix race condition with destroying of vcc From: David Woodhouse To: Krzysztof Mazur Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 30 Oct 2012 09:37:48 +0000 In-Reply-To: <1350926091-12642-2-git-send-email-krzysiek@podlesie.net> References: <1350926091-12642-1-git-send-email-krzysiek@podlesie.net> <1350926091-12642-2-git-send-email-krzysiek@podlesie.net> Content-Type: multipart/signed; micalg="sha1"; protocol="application/x-pkcs7-signature"; boundary="=-cSUV3jzXKcZUxKqLnAVL" X-Mailer: Evolution 3.6.1 (3.6.1-1.fc18) Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9953 Lines: 156 --=-cSUV3jzXKcZUxKqLnAVL Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2012-10-22 at 19:14 +0200, Krzysztof Mazur wrote: > The pppoatm_send() calls vcc->send() and now also checks for > some vcc flags that indicate destroyed vcc without proper locking. >=20 > 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. >=20 > The pppoatm_send() is called with BH disabled, so bh_lock_sock() > should be used instead of lock_sock(). Should we be locking it earlier, so that the atm_may_send() call is also covered by the lock? Either way, it's an obvious improvement on what we had before =E2=80=94 and= even if the answer to my question above is 'yes', exceeding the configured size by one packet is both harmless and almost never going to happen since we now limit ourselves to two packets anyway. 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