From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E36C9C43460 for ; Thu, 22 Apr 2021 10:49:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AA69D61428 for ; Thu, 22 Apr 2021 10:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235988AbhDVKuP (ORCPT ); Thu, 22 Apr 2021 06:50:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:56580 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235800AbhDVKuL (ORCPT ); Thu, 22 Apr 2021 06:50:11 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 90C8D61452; Thu, 22 Apr 2021 10:49:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1619088576; bh=L4VyomxmbGQvJRnBwxrzKMAjbER+ODVjPhNRkTmCL18=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WiyZHUkDt6lTkMgFX2mROlI6MmKohfSE9/YMdQVe9vjTTwc9442w0H8vGLHlgLRqe +70Hjp7wvwkfLmwK7nuEA5Xvf8zKFQkAB+zB7iMjUv9/A3yNPGnmj51P6C+IJK0h1C C4oVRMubBN9kBEpHHoHZx5vno2mT7r1xbnwvazZG2D7fsKxw7cYFWtQveabj+2lymY yWyvC3xLx394Kc3BmgZRKKbhNm3G7nmMjHARPu0FqQwK/W2TRDR/OOOMq9/DPP5GwS ewInPasiaATqU7iRr92Rh8tqzMmCF6X1kli9JNSJeHyQwevi33V3v+ntu0pG8PZOwM ZhUcqrgOjveLQ== Date: Thu, 22 Apr 2021 13:49:32 +0300 From: Leon Romanovsky To: Loic Poulain Cc: kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org Subject: Re: [PATCH net-next] net: wwan: core: Return poll error in case of port removal Message-ID: References: <1619084614-24925-1-git-send-email-loic.poulain@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1619084614-24925-1-git-send-email-loic.poulain@linaro.org> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Apr 22, 2021 at 11:43:34AM +0200, Loic Poulain wrote: > Ensure that the poll system call returns error flags when port is > removed, allowing user side to properly fail, without trying read > or write. Port removal leads to nullified port operations, add a > is_port_connected() helper to safely check the status. > > Fixes: 9a44c1cc6388 ("net: Add a WWAN subsystem") > Signed-off-by: Loic Poulain > --- > drivers/net/wwan/wwan_core.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c > index 5be5e1e..c965b21 100644 > --- a/drivers/net/wwan/wwan_core.c > +++ b/drivers/net/wwan/wwan_core.c > @@ -369,14 +369,25 @@ static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb) > return ret; > } > > +static bool is_port_connected(struct wwan_port *port) > +{ > + bool connected; > + > + mutex_lock(&port->ops_lock); > + connected = !!port->ops; > + mutex_unlock(&port->ops_lock); > + > + return connected; > +} The above can't be correct. What prevents to change the status of port->ops right before or after your mutex_lock/mutex_unlock? > + > static bool is_read_blocked(struct wwan_port *port) > { > - return skb_queue_empty(&port->rxq) && port->ops; > + return skb_queue_empty(&port->rxq) && is_port_connected(port); > } > > static bool is_write_blocked(struct wwan_port *port) > { > - return test_bit(WWAN_PORT_TX_OFF, &port->flags) && port->ops; > + return test_bit(WWAN_PORT_TX_OFF, &port->flags) && is_port_connected(port); > } > > static int wwan_wait_rx(struct wwan_port *port, bool nonblock) > @@ -508,6 +519,8 @@ static __poll_t wwan_port_fops_poll(struct file *filp, poll_table *wait) > mask |= EPOLLOUT | EPOLLWRNORM; > if (!is_read_blocked(port)) > mask |= EPOLLIN | EPOLLRDNORM; > + if (!is_port_connected(port)) > + mask |= EPOLLHUP | EPOLLERR; > > return mask; > } > -- > 2.7.4 >