From patchwork Mon Mar 6 12:01:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhong Jinghua X-Patchwork-Id: 659673 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 B1A7EC678D4 for ; Mon, 6 Mar 2023 11:38:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230272AbjCFLic (ORCPT ); Mon, 6 Mar 2023 06:38:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230256AbjCFLib (ORCPT ); Mon, 6 Mar 2023 06:38:31 -0500 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE8D61993; Mon, 6 Mar 2023 03:38:17 -0800 (PST) Received: from kwepemm600002.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4PVc5Z4NNTz1gwqh; Mon, 6 Mar 2023 19:38:10 +0800 (CST) Received: from localhost.localdomain (10.175.127.227) by kwepemm600002.china.huawei.com (7.193.23.29) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Mon, 6 Mar 2023 19:38:15 +0800 From: Zhong Jinghua To: , CC: , , , , Subject: [PATCH-next v2] scsi: fix use-after-free problem in scsi_remove_target Date: Mon, 6 Mar 2023 20:01:28 +0800 Message-ID: <20230306120128.3158269-1-zhongjinghua@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm600002.china.huawei.com (7.193.23.29) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org A use-after-free problem like below: BUG: KASAN: use-after-free in scsi_target_reap+0x6c/0x70 Workqueue: scsi_wq_1 __iscsi_unbind_session [scsi_transport_iscsi] Call trace: dump_backtrace+0x0/0x320 show_stack+0x24/0x30 dump_stack+0xdc/0x128 print_address_description+0x68/0x278 kasan_report+0x1e4/0x308 __asan_report_load4_noabort+0x30/0x40 scsi_target_reap+0x6c/0x70 scsi_remove_target+0x430/0x640 __iscsi_unbind_session+0x164/0x268 [scsi_transport_iscsi] process_one_work+0x67c/0x1350 worker_thread+0x370/0xf90 kthread+0x2a4/0x320 ret_from_fork+0x10/0x18 The problem is caused by a concurrency scenario: T0: delete target // echo 1 > /sys/devices/platform/host1/session1/target1:0:0/1:0:0:1/delete T1: logout // iscsiadm -m node --logout T0 T1 sdev_store_delete scsi_remove_device device_remove_file __scsi_remove_device __iscsi_unbind_session scsi_remove_target spin_lock_irqsave list_for_each_entry scsi_target_reap // starget->reap_ref 1 -> 0 kref_get(&starget->reap_ref); // warn use-after-free. spin_unlock_irqrestore scsi_target_reap_ref_release scsi_target_destroy ... // delete starget scsi_target_reap // UAF When T0 reduces the reference count to 0, but has not been released, T1 can still enter list_for_each_entry, and then kref_get reports UAF. Fix it by using kref_get_unless_zero() to check for a reference count of 0. Signed-off-by: Zhong Jinghua --- v2: commit message: "starget->reaf" -> "starget->reap_ref" comment: "If it is reduced to 0, it means that other processes are releasing it and there is no need to delete it again" -> "If the reference count is already zero, skip this target is safe because scsi_target_destroy() will wait until the host lock has been released before freeing starget." drivers/scsi/scsi_sysfs.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index e7893835b99a..12e8ed6d55cb 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1561,7 +1561,16 @@ void scsi_remove_target(struct device *dev) starget->state == STARGET_CREATED_REMOVE) continue; if (starget->dev.parent == dev || &starget->dev == dev) { - kref_get(&starget->reap_ref); + + /* + * If the reference count is already zero, skip this + * target is safe because scsi_target_destroy() + * will wait until the host lock has been released + * before freeing starget. + */ + if (!kref_get_unless_zero(&starget->reap_ref)) + continue; + if (starget->state == STARGET_CREATED) starget->state = STARGET_CREATED_REMOVE; else