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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC575C19F28 for ; Wed, 27 Jul 2022 16:47:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240163AbiG0Qrv (ORCPT ); Wed, 27 Jul 2022 12:47:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240058AbiG0Qq7 (ORCPT ); Wed, 27 Jul 2022 12:46:59 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AE3852DFD; Wed, 27 Jul 2022 09:32:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 14E1AB821BA; Wed, 27 Jul 2022 16:31:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62F5DC433D6; Wed, 27 Jul 2022 16:31:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1658939517; bh=htyf8dAJwRiQSesYEE98VZHxac6Wn8C8lGyj2NnpPXs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V6apZ4crY5cQCt0bJ4N3PUwk7XBT98FL/ho28gE+2DHOrZxEZ2P2KmtZ9KcyZ18P4 pO7NlrxZaFix0aCUhSdfa++EXaEn3jMuRM1CIepuYtjaLlvAxbi69Ouj81+v7iyB3W a9bVghNeeQhmiS0lP5Fgy6FhhYn3mFcLwd0lOLvY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jakub Kicinski , Fedor Pchelkin Subject: [PATCH 5.10 010/105] net: make free_netdev() more lenient with unregistering devices Date: Wed, 27 Jul 2022 18:09:56 +0200 Message-Id: <20220727161012.480155559@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220727161012.056867467@linuxfoundation.org> References: <20220727161012.056867467@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Fedor Pchelkin From: Jakub Kicinski commit c269a24ce057abfc31130960e96ab197ef6ab196 upstream. There are two flavors of handling netdev registration: - ones called without holding rtnl_lock: register_netdev() and unregister_netdev(); and - those called with rtnl_lock held: register_netdevice() and unregister_netdevice(). While the semantics of the former are pretty clear, the same can't be said about the latter. The netdev_todo mechanism is utilized to perform some of the device unregistering tasks and it hooks into rtnl_unlock() so the locked variants can't actually finish the work. In general free_netdev() does not mix well with locked calls. Most drivers operating under rtnl_lock set dev->needs_free_netdev to true and expect core to make the free_netdev() call some time later. The part where this becomes most problematic is error paths. There is no way to unwind the state cleanly after a call to register_netdevice(), since unreg can't be performed fully without dropping locks. Make free_netdev() more lenient, and defer the freeing if device is being unregistered. This allows error paths to simply call free_netdev() both after register_netdevice() failed, and after a call to unregister_netdevice() but before dropping rtnl_lock. Simplify the error paths which are currently doing gymnastics around free_netdev() handling. Signed-off-by: Jakub Kicinski Signed-off-by: Fedor Pchelkin Signed-off-by: Greg Kroah-Hartman --- net/8021q/vlan.c | 4 +--- net/core/dev.c | 11 +++++++++++ net/core/rtnetlink.c | 23 ++++++----------------- 3 files changed, 18 insertions(+), 20 deletions(-) --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -278,9 +278,7 @@ static int register_vlan_device(struct n return 0; out_free_newdev: - if (new_dev->reg_state == NETREG_UNINITIALIZED || - new_dev->reg_state == NETREG_UNREGISTERED) - free_netdev(new_dev); + free_netdev(new_dev); return err; } --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10683,6 +10683,17 @@ void free_netdev(struct net_device *dev) struct napi_struct *p, *n; might_sleep(); + + /* When called immediately after register_netdevice() failed the unwind + * handling may still be dismantling the device. Handle that case by + * deferring the free. + */ + if (dev->reg_state == NETREG_UNREGISTERING) { + ASSERT_RTNL(); + dev->needs_free_netdev = true; + return; + } + netif_free_tx_queues(dev); netif_free_rx_queues(dev); --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -3442,26 +3442,15 @@ replay: dev->ifindex = ifm->ifi_index; - if (ops->newlink) { + if (ops->newlink) err = ops->newlink(link_net ? : net, dev, tb, data, extack); - /* Drivers should set dev->needs_free_netdev - * and unregister it on failure after registration - * so that device could be finally freed in rtnl_unlock. - */ - if (err < 0) { - /* If device is not registered at all, free it now */ - if (dev->reg_state == NETREG_UNINITIALIZED || - dev->reg_state == NETREG_UNREGISTERED) - free_netdev(dev); - goto out; - } - } else { + else err = register_netdevice(dev); - if (err < 0) { - free_netdev(dev); - goto out; - } + if (err < 0) { + free_netdev(dev); + goto out; } + err = rtnl_configure_link(dev, ifm); if (err < 0) goto out_unregister;