From patchwork Thu Mar 30 08:29:54 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Nicholas A. Bellinger" X-Patchwork-Id: 9653217 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A96866034C for ; Thu, 30 Mar 2017 08:32:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9A7DA2679B for ; Thu, 30 Mar 2017 08:32:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8ECB3284D5; Thu, 30 Mar 2017 08:32:55 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3D6C22679B for ; Thu, 30 Mar 2017 08:32:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753059AbdC3IaH (ORCPT ); Thu, 30 Mar 2017 04:30:07 -0400 Received: from mail.linux-iscsi.org ([67.23.28.174]:47724 "EHLO linux-iscsi.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751394AbdC3IaC (ORCPT ); Thu, 30 Mar 2017 04:30:02 -0400 Received: from linux-iscsi.org (localhost [127.0.0.1]) by linux-iscsi.org (Postfix) with ESMTP id DD4F740B05; Thu, 30 Mar 2017 08:30:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=linux-iscsi.org; s=default.private; t=1490862600; bh=wCXHcxwFOG3NIlPuvmrqNbNAKANcV7j hn16iHNLERQ0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To: References; b=boPkv5CCpRy8Z3dYmu14mN0X05sg45ssA/wwg5rSxzd65YP/Djfe 3cNK08Bx4fY6rt3iYkrkCmqVK43mprr3deFXH6m/o3fH+xPddBUVL7J/xyrJJqATTBk ttMtHsCd91PXc7T8GmwMxCNv9fhj6RFadp8pSzo0tY/Ymm0fASJg= From: "Nicholas A. Bellinger" To: target-devel Cc: linux-scsi , lkml , Rob Millner , Chu Yuan Lin , James Shen , Nicholas Bellinger Subject: [PATCH 2/2] target: Avoid mappedlun symlink creation during lun shutdown Date: Thu, 30 Mar 2017 08:29:54 +0000 Message-Id: <1490862594-2712-3-git-send-email-nab@linux-iscsi.org> X-Mailer: git-send-email 1.7.2.5 In-Reply-To: <1490862594-2712-1-git-send-email-nab@linux-iscsi.org> References: <1490862594-2712-1-git-send-email-nab@linux-iscsi.org> Sender: target-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: target-devel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Nicholas Bellinger This patch closes a race between se_lun deletion during configfs unlink in target_fabric_port_unlink() -> core_dev_del_lun() -> core_tpg_remove_lun(), when transport_clear_lun_ref() blocks waiting for percpu_ref RCU grace period to finish, but a new NodeACL mappedlun is added before the RCU grace period has completed. This can happen in target_fabric_mappedlun_link() because it only checks for se_lun->lun_se_dev, which is not cleared until after transport_clear_lun_ref() percpu_ref RCU grace period finishes. This bug originally manifested as NULL pointer dereference OOPsen in target_stat_scsi_att_intr_port_show_attr_dev() on v4.1.y code, because it dereferences lun->lun_se_dev without a explicit NULL pointer check. In post v4.1 code with target-core RCU conversion, the code in target_stat_scsi_att_intr_port_show_attr_dev() no longer uses se_lun->lun_se_dev, but the same race still exists. To address the bug, go ahead and set se_lun>lun_shutdown as early as possible in core_tpg_remove_lun(), and ensure new NodeACL mappedlun creation in target_fabric_mappedlun_link() fails during se_lun shutdown. Reported-by: James Shen Cc: James Shen Tested-by: James Shen Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_fabric_configfs.c | 5 +++++ drivers/target/target_core_tpg.c | 4 ++++ include/target/target_core_base.h | 1 + 3 files changed, 10 insertions(+) diff --git a/drivers/target/target_core_fabric_configfs.c b/drivers/target/target_core_fabric_configfs.c index d8a16ca..d1e6cab 100644 --- a/drivers/target/target_core_fabric_configfs.c +++ b/drivers/target/target_core_fabric_configfs.c @@ -92,6 +92,11 @@ static int target_fabric_mappedlun_link( pr_err("Source se_lun->lun_se_dev does not exist\n"); return -EINVAL; } + if (lun->lun_shutdown) { + pr_err("Unable to create mappedlun symlink because" + " lun->lun_shutdown=true\n"); + return -EINVAL; + } se_tpg = lun->lun_tpg; nacl_ci = &lun_acl_ci->ci_parent->ci_group->cg_item; diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c index 6fb1919..dfaef4d 100644 --- a/drivers/target/target_core_tpg.c +++ b/drivers/target/target_core_tpg.c @@ -642,6 +642,8 @@ void core_tpg_remove_lun( */ struct se_device *dev = rcu_dereference_raw(lun->lun_se_dev); + lun->lun_shutdown = true; + core_clear_lun_from_tpg(lun, tpg); /* * Wait for any active I/O references to percpu se_lun->lun_ref to @@ -663,6 +665,8 @@ void core_tpg_remove_lun( } if (!(dev->se_hba->hba_flags & HBA_FLAGS_INTERNAL_USE)) hlist_del_rcu(&lun->link); + + lun->lun_shutdown = false; mutex_unlock(&tpg->tpg_lun_mutex); percpu_ref_exit(&lun->lun_ref); diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h index 4b784b6..2e28246 100644 --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -705,6 +705,7 @@ struct se_lun { u64 unpacked_lun; #define SE_LUN_LINK_MAGIC 0xffff7771 u32 lun_link_magic; + bool lun_shutdown; bool lun_access_ro; u32 lun_index;