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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 4C8B3C55186 for ; Wed, 22 Apr 2020 10:39:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B71A2073A for ; Wed, 22 Apr 2020 10:39:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587551956; bh=dUEfWMtiuAicjjPNhOpc86+qxyFCQ0oSenl0428WBpw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=bCDGLgItPk9pf4/fFRNjZGPbHbQbZ5pZAOTPN8/iTkH6SlktonlhFh8P4b6hJtIII 1bGwlSCSObTshkSA6EZ7ESNdlBNm4mkBehdvMDORw/qaBBYrjir4nccTkirfbu+NCn 6kUuSOSMrXyB9D/vT6tlkzojvbYCFXbtrL4P/lc4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730935AbgDVKjO (ORCPT ); Wed, 22 Apr 2020 06:39:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:57916 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729434AbgDVKV3 (ORCPT ); Wed, 22 Apr 2020 06:21:29 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 84CB820784; Wed, 22 Apr 2020 10:21:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587550889; bh=dUEfWMtiuAicjjPNhOpc86+qxyFCQ0oSenl0428WBpw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gX6nY0SfEYtGO83Mv+V/OD/k+Uw1TMYOPwYZoIv2nDNntFSW72ml+5kyOKjRLjfyM Qt8TQKWNZC2NLjS2TOaYWTdA72huSwzPYnHMZio0ufq41G3FAA9Gq+MWm6riivQ2EM pTF8Q3gmmrqYNvCmIHQdbVToW9C9Lg4HQwywjlVU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ilya Dryomov , Jason Dillaman Subject: [PATCH 5.6 016/166] rbd: avoid a deadlock on header_rwsem when flushing notifies Date: Wed, 22 Apr 2020 11:55:43 +0200 Message-Id: <20200422095050.121296682@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200422095047.669225321@linuxfoundation.org> References: <20200422095047.669225321@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ilya Dryomov commit 0e4e1de5b63fa423b13593337a27fd2d2b0bcf77 upstream. rbd_unregister_watch() flushes notifies and therefore cannot be called under header_rwsem because a header update notify takes header_rwsem to synchronize with "rbd map". If mapping an image fails after the watch is established and a header update notify sneaks in, we deadlock when erroring out from rbd_dev_image_probe(). Move watch registration and unregistration out of the critical section. The only reason they were put there was to make header_rwsem management slightly more obvious. Fixes: 811c66887746 ("rbd: fix rbd map vs notify races") Signed-off-by: Ilya Dryomov Reviewed-by: Jason Dillaman Signed-off-by: Greg Kroah-Hartman --- drivers/block/rbd.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -4554,6 +4554,10 @@ static void cancel_tasks_sync(struct rbd cancel_work_sync(&rbd_dev->unlock_work); } +/* + * header_rwsem must not be held to avoid a deadlock with + * rbd_dev_refresh() when flushing notifies. + */ static void rbd_unregister_watch(struct rbd_device *rbd_dev) { cancel_tasks_sync(rbd_dev); @@ -6964,6 +6968,9 @@ static void rbd_dev_image_release(struct * device. If this image is the one being mapped (i.e., not a * parent), initiate a watch on its header object before using that * object to get detailed information about the rbd image. + * + * On success, returns with header_rwsem held for write if called + * with @depth == 0. */ static int rbd_dev_image_probe(struct rbd_device *rbd_dev, int depth) { @@ -6993,6 +7000,9 @@ static int rbd_dev_image_probe(struct rb } } + if (!depth) + down_write(&rbd_dev->header_rwsem); + ret = rbd_dev_header_info(rbd_dev); if (ret) { if (ret == -ENOENT && !need_watch) @@ -7044,6 +7054,8 @@ static int rbd_dev_image_probe(struct rb err_out_probe: rbd_dev_unprobe(rbd_dev); err_out_watch: + if (!depth) + up_write(&rbd_dev->header_rwsem); if (need_watch) rbd_unregister_watch(rbd_dev); err_out_format: @@ -7107,12 +7119,9 @@ static ssize_t do_rbd_add(struct bus_typ goto err_out_rbd_dev; } - down_write(&rbd_dev->header_rwsem); rc = rbd_dev_image_probe(rbd_dev, 0); - if (rc < 0) { - up_write(&rbd_dev->header_rwsem); + if (rc < 0) goto err_out_rbd_dev; - } if (rbd_dev->opts->alloc_size > rbd_dev->layout.object_size) { rbd_warn(rbd_dev, "alloc_size adjusted to %u",