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 7055FC32771 for ; Mon, 26 Sep 2022 10:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233348AbiIZKRL (ORCPT ); Mon, 26 Sep 2022 06:17:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234779AbiIZKQS (ORCPT ); Mon, 26 Sep 2022 06:16:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FD9B10043; Mon, 26 Sep 2022 03:14:42 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 3919F60B4A; Mon, 26 Sep 2022 10:14:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30150C43470; Mon, 26 Sep 2022 10:14:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1664187281; bh=dgTzuXvWpBNqEIEFup/8PQSrW0v3ksBIqp3m5roA2og=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N5Usqd5MU31VYDwWVLCggktKSBb5GlkxcvYJLToSq3EXynsv/2trBFBygA9FZP3SV E5wmXB2ajlJ2YCfn0D1Ja/czFFg0UyMPZRcxqWtRKWfmMiWQLI9DbrVRm3hpxi7ss1 IuRdeuYc4Fs0bgWvydS83XH4GJpZAtTiwqlwqsWA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefan Haberland , Jan Hoeppner , Jens Axboe Subject: [PATCH 4.9 28/30] s390/dasd: fix Oops in dasd_alias_get_start_dev due to missing pavgroup Date: Mon, 26 Sep 2022 12:11:59 +0200 Message-Id: <20220926100737.151359246@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220926100736.153157100@linuxfoundation.org> References: <20220926100736.153157100@linuxfoundation.org> User-Agent: quilt/0.67 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: Stefan Haberland commit db7ba07108a48c0f95b74fabbfd5d63e924f992d upstream. Fix Oops in dasd_alias_get_start_dev() function caused by the pavgroup pointer being NULL. The pavgroup pointer is checked on the entrance of the function but without the lcu->lock being held. Therefore there is a race window between dasd_alias_get_start_dev() and _lcu_update() which sets pavgroup to NULL with the lcu->lock held. Fix by checking the pavgroup pointer with lcu->lock held. Cc: # 2.6.25+ Fixes: 8e09f21574ea ("[S390] dasd: add hyper PAV support to DASD device driver, part 1") Signed-off-by: Stefan Haberland Reviewed-by: Jan Hoeppner Link: https://lore.kernel.org/r/20220919154931.4123002-2-sth@linux.ibm.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/s390/block/dasd_alias.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/drivers/s390/block/dasd_alias.c +++ b/drivers/s390/block/dasd_alias.c @@ -674,12 +674,12 @@ int dasd_alias_remove_device(struct dasd struct dasd_device *dasd_alias_get_start_dev(struct dasd_device *base_device) { struct dasd_eckd_private *alias_priv, *private = base_device->private; - struct alias_pav_group *group = private->pavgroup; struct alias_lcu *lcu = private->lcu; struct dasd_device *alias_device; + struct alias_pav_group *group; unsigned long flags; - if (!group || !lcu) + if (!lcu) return NULL; if (lcu->pav == NO_PAV || lcu->flags & (NEED_UAC_UPDATE | UPDATE_PENDING)) @@ -696,6 +696,11 @@ struct dasd_device *dasd_alias_get_start } spin_lock_irqsave(&lcu->lock, flags); + group = private->pavgroup; + if (!group) { + spin_unlock_irqrestore(&lcu->lock, flags); + return NULL; + } alias_device = group->next; if (!alias_device) { if (list_empty(&group->aliaslist)) {