Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753165AbdC3IaI (ORCPT ); Thu, 30 Mar 2017 04:30:08 -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 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3214 Lines: 90 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; -- 1.9.1