From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38530 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751499AbdITJUO (ORCPT ); Wed, 20 Sep 2017 05:20:14 -0400 Subject: Patch "smp/hotplug: Handle removal correctly in cpuhp_store_callbacks()" has been added to the 4.13-stable tree To: Ethan.Barnes@wdc.com, bigeasy@linutronix.d, ethan.barnes@sandisk.com, gregkh@linuxfoundation.org, mingo@kernel.or, paulmck@linux.vnet.ibm.com, srivatsa@mit.edu, tglx@linutronix.de Cc: , From: Date: Wed, 20 Sep 2017 11:20:09 +0200 Message-ID: <150589920953140@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled smp/hotplug: Handle removal correctly in cpuhp_store_callbacks() to the 4.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: smp-hotplug-handle-removal-correctly-in-cpuhp_store_callbacks.patch and it can be found in the queue-4.13 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 0c96b27305faf06c068b45e07d28336c80dac286 Mon Sep 17 00:00:00 2001 From: Ethan Barnes Date: Wed, 19 Jul 2017 22:36:00 +0000 Subject: smp/hotplug: Handle removal correctly in cpuhp_store_callbacks() 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; Patches currently in stable-queue which might be from Ethan.Barnes@wdc.com are queue-4.13/smp-hotplug-handle-removal-correctly-in-cpuhp_store_callbacks.patch