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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 482A6C63697 for ; Tue, 17 Nov 2020 13:11:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E18172225B for ; Tue, 17 Nov 2020 13:11:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="B+mljd6g" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729209AbgKQNLF (ORCPT ); Tue, 17 Nov 2020 08:11:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:40272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729553AbgKQNK4 (ORCPT ); Tue, 17 Nov 2020 08:10:56 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (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 027F82225B; Tue, 17 Nov 2020 13:10:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605618655; bh=fOenn9yeBaHCunCysCslJG4dwffDPlwPlsVozQjgGfA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B+mljd6gQfu+k5OdZe9sPfpzv1upmSFjJVMe/ugu855NCbP9y5+Zie2FNzO2Aa4sN vsKxf8BKgckniZ9KKbC64i5X/MGfxUbhEO0DwQURpg65JwI7WrLkOO5W8DR5YoW17A x+Sa9wbpNRciLmyDisfVly8k+tTl56c0nvAKQbSE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Brian Bunker , Jitendra Khasdev , Hannes Reinecke , "Martin K. Petersen" , Sasha Levin Subject: [PATCH 4.9 34/78] scsi: scsi_dh_alua: Avoid crash during alua_bus_detach() Date: Tue, 17 Nov 2020 14:05:00 +0100 Message-Id: <20201117122110.773594142@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201117122109.116890262@linuxfoundation.org> References: <20201117122109.116890262@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: linux-kernel@vger.kernel.org From: Hannes Reinecke [ Upstream commit 5faf50e9e9fdc2117c61ff7e20da49cd6a29e0ca ] alua_bus_detach() might be running concurrently with alua_rtpg_work(), so we might trip over h->sdev == NULL and call BUG_ON(). The correct way of handling it is to not set h->sdev to NULL in alua_bus_detach(), and call rcu_synchronize() before the final delete to ensure that all concurrent threads have left the critical section. Then we can get rid of the BUG_ON() and replace it with a simple if condition. Link: https://lore.kernel.org/r/1600167537-12509-1-git-send-email-jitendra.khasdev@oracle.com Link: https://lore.kernel.org/r/20200924104559.26753-1-hare@suse.de Cc: Brian Bunker Acked-by: Brian Bunker Tested-by: Jitendra Khasdev Reviewed-by: Jitendra Khasdev Signed-off-by: Hannes Reinecke Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/scsi/device_handler/scsi_dh_alua.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c index 60c288526355a..2bc3dc6244a5e 100644 --- a/drivers/scsi/device_handler/scsi_dh_alua.c +++ b/drivers/scsi/device_handler/scsi_dh_alua.c @@ -657,8 +657,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg) rcu_read_lock(); list_for_each_entry_rcu(h, &tmp_pg->dh_list, node) { - /* h->sdev should always be valid */ - BUG_ON(!h->sdev); + if (!h->sdev) + continue; h->sdev->access_state = desc[0]; } rcu_read_unlock(); @@ -704,7 +704,8 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg) pg->expiry = 0; rcu_read_lock(); list_for_each_entry_rcu(h, &pg->dh_list, node) { - BUG_ON(!h->sdev); + if (!h->sdev) + continue; h->sdev->access_state = (pg->state & SCSI_ACCESS_STATE_MASK); if (pg->pref) @@ -1149,7 +1150,6 @@ static void alua_bus_detach(struct scsi_device *sdev) spin_lock(&h->pg_lock); pg = h->pg; rcu_assign_pointer(h->pg, NULL); - h->sdev = NULL; spin_unlock(&h->pg_lock); if (pg) { spin_lock_irq(&pg->lock); @@ -1158,6 +1158,7 @@ static void alua_bus_detach(struct scsi_device *sdev) kref_put(&pg->kref, release_port_group); } sdev->handler_data = NULL; + synchronize_rcu(); kfree(h); } -- 2.27.0