Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755544AbaBKUaZ (ORCPT ); Tue, 11 Feb 2014 15:30:25 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:39869 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753256AbaBKTGN (ORCPT ); Tue, 11 Feb 2014 14:06:13 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tommy Apel , Nicholas Bellinger Subject: [PATCH 3.13 087/120] target: Fix percpu_ref_put race in transport_lun_remove_cmd Date: Tue, 11 Feb 2014 11:05:28 -0800 Message-Id: <20140211184826.094276598@linuxfoundation.org> X-Mailer: git-send-email 1.8.5.1.163.gd7aced9 In-Reply-To: <20140211184823.492407127@linuxfoundation.org> References: <20140211184823.492407127@linuxfoundation.org> User-Agent: quilt/0.61-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nicholas Bellinger commit 5259a06ef97068b710f45d092a587e8d740f750f upstream. This patch fixes a percpu_ref_put race for se_lun->lun_ref in transport_lun_remove_cmd() where ->lun_ref could end up being put more than once per command via different target completion and fabric release contexts. It adds a cmpxchg() for se_cmd->lun_ref_active to ensure that percpu_ref_put() is only ever called once per se_cmd. This bug was manifesting itself as a LUN shutdown regression bug in >= v3.13 code, where percpu_ref_kill() would end up hanging indefinately due to the incorrect percpu_ref count. (Change se_cmd->lun_ref_active from bool -> int to force at least a 4-byte cmpxchg with MIPS ll/sc ins. - Fengguang) Reported-by: Tommy Apel Cc: Tommy Apel Signed-off-by: Nicholas Bellinger Signed-off-by: Greg Kroah-Hartman --- drivers/target/target_core_transport.c | 5 +++-- include/target/target_core_base.h | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) --- a/drivers/target/target_core_transport.c +++ b/drivers/target/target_core_transport.c @@ -568,10 +568,11 @@ static void transport_lun_remove_cmd(str { struct se_lun *lun = cmd->se_lun; - if (!lun || !cmd->lun_ref_active) + if (!lun) return; - percpu_ref_put(&lun->lun_ref); + if (cmpxchg(&cmd->lun_ref_active, true, false)) + percpu_ref_put(&lun->lun_ref); } void transport_cmd_finish_abort(struct se_cmd *cmd, int remove) --- a/include/target/target_core_base.h +++ b/include/target/target_core_base.h @@ -497,7 +497,7 @@ struct se_cmd { void *priv; /* Used for lun->lun_ref counting */ - bool lun_ref_active; + int lun_ref_active; }; struct se_ua { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/