Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933042AbdIXUlM (ORCPT ); Sun, 24 Sep 2017 16:41:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60448 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932649AbdIXUlF (ORCPT ); Sun, 24 Sep 2017 16:41:05 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ethan Barnes , Thomas Gleixner , Ingo Molnar , "Srivatsa S. Bhat" , Sebastian Siewior , Paul McKenney Subject: [PATCH 4.13 007/109] smp/hotplug: Handle removal correctly in cpuhp_store_callbacks() Date: Sun, 24 Sep 2017 22:32:28 +0200 Message-Id: <20170924203353.398937718@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170924203353.104695385@linuxfoundation.org> References: <20170924203353.104695385@linuxfoundation.org> User-Agent: quilt/0.65 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 Content-Length: 2495 Lines: 64 4.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ethan Barnes commit 0c96b27305faf06c068b45e07d28336c80dac286 upstream. If cpuhp_store_callbacks() is called for CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN, which are the indicators for dynamically allocated states, then cpuhp_store_callbacks() allocates a new dynamic state. The first allocation in each range returns CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN. If cpuhp_remove_state() is invoked for one of these states, then there is no protection against the allocation mechanism. So the removal, which should clear the callbacks and the name, gets a new state assigned and clears that one. As a consequence the state which should be cleared stays initialized. A consecutive CPU hotplug operation dereferences the state callbacks and accesses either freed or reused memory, resulting in crashes. Add a protection against this by checking the name argument for NULL. If it's NULL it's a removal. If not, it's an allocation. [ tglx: Added a comment and massaged changelog ] Fixes: 5b7aa87e0482 ("cpu/hotplug: Implement setup/removal interface") Signed-off-by: Ethan Barnes Signed-off-by: Thomas Gleixner Cc: Ingo Molnar Cc: "Srivatsa S. Bhat" Cc: Sebastian Siewior Cc: Paul McKenney Link: http://lkml.kernel.org/r/DM2PR04MB398242FC7776D603D9F99C894A60@DM2PR04MB398.namprd04.prod.outlook.com Signed-off-by: Greg Kroah-Hartman --- kernel/cpu.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1252,7 +1252,17 @@ static int cpuhp_store_callbacks(enum cp struct cpuhp_step *sp; int ret = 0; - if (state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN) { + /* + * If name is NULL, then the state gets removed. + * + * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on + * the first allocation from these dynamic ranges, so the removal + * would trigger a new allocation and clear the wrong (already + * empty) state, leaving the callbacks of the to be cleared state + * dangling, which causes wreckage on the next hotplug operation. + */ + if (name && (state == CPUHP_AP_ONLINE_DYN || + state == CPUHP_BP_PREPARE_DYN)) { ret = cpuhp_reserve_state(state); if (ret < 0) return ret;