Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751961AbaKIOHK (ORCPT ); Sun, 9 Nov 2014 09:07:10 -0500 Received: from relay.parallels.com ([195.214.232.42]:53613 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751788AbaKIOHI (ORCPT ); Sun, 9 Nov 2014 09:07:08 -0500 Message-ID: <1415542020.474.22.camel@tkhai> Subject: Re: [PATCH v4] sched/numa: fix unsafe get_task_struct() in task_numa_assign() From: Kirill Tkhai To: Sasha Levin CC: , Peter Zijlstra , Oleg Nesterov , Ingo Molnar , "Vladimir Davydov" , Kirill Tkhai Date: Sun, 9 Nov 2014 17:07:00 +0300 In-Reply-To: <545D928B.2070508@oracle.com> References: <1413962231.19914.130.camel@tkhai> <545D928B.2070508@oracle.com> Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, В Пт, 07/11/2014 в 22:48 -0500, Sasha Levin пишет: > On 10/22/2014 03:17 AM, Kirill Tkhai wrote: > > Unlocked access to dst_rq->curr in task_numa_compare() is racy. > > If curr task is exiting this may be a reason of use-after-free: > [...] > > I've complained about an unrelated issue in that part of the code > a while back (https://lkml.org/lkml/2014/5/12/508) which PeterZ > ended up fixing (https://lkml.org/lkml/2014/5/21/428) but it seems > that both of us forgot to follow up on that and the fix never got > upstream. > > Ever since this patch made it upstream, Peter's patch which I was > carrying in my tree stopped applying and I've started seeing: > > [ 829.539183] BUG: spinlock recursion on CPU#10, trinity-c594/11067 > [ 829.539203] lock: 0xffff880631dd6b80, .magic: dead4ead, .owner: trinity-c594/11067, .owner_cpu: 13 > [ 829.539212] CPU: 10 PID: 11067 Comm: trinity-c594 Not tainted 3.18.0-rc3-next-20141106-sasha-00054-g09b7ccf-dirty #1448 > [ 829.539226] 0000000000000000 0000000000000000 ffff880053acb000 ffff88032b71f828 > [ 829.539235] ffffffffa009fb5a 0000000000000057 ffff880631dd6b80 ffff88032b71f868 > [ 829.539243] ffffffff963f0c57 ffff880053acbd80 ffff880053acbdb0 ffff88032b71f858 > [ 829.539246] Call Trace: > [ 829.539265] dump_stack (lib/dump_stack.c:52) > [ 829.539277] spin_dump (kernel/locking/spinlock_debug.c:68 (discriminator 8)) > [ 829.539282] spin_bug (kernel/locking/spinlock_debug.c:76) > [ 829.539288] do_raw_spin_lock (kernel/locking/spinlock_debug.c:84 kernel/locking/spinlock_debug.c:135) > [ 829.539304] ? __schedule (kernel/sched/core.c:2803) > [ 829.539313] _raw_spin_lock_irq (include/linux/spinlock_api_smp.h:129 kernel/locking/spinlock.c:167) > [ 829.539321] ? task_numa_find_cpu (kernel/sched/fair.c:1258 kernel/sched/fair.c:1385) > [ 829.539330] ? rcu_is_watching (./arch/x86/include/asm/preempt.h:95 kernel/rcu/tree.c:827) > [ 829.539336] task_numa_find_cpu (kernel/sched/fair.c:1258 kernel/sched/fair.c:1385) > [ 829.539342] ? task_numa_find_cpu (kernel/sched/fair.c:1253 kernel/sched/fair.c:1385) > [ 829.539352] ? preempt_count_sub (kernel/sched/core.c:2644) > [ 829.539358] task_numa_migrate (kernel/sched/fair.c:1452) > [ 829.539364] ? task_numa_migrate (kernel/sched/fair.c:1391) > [ 829.539376] ? kvm_clock_read (./arch/x86/include/asm/preempt.h:87 arch/x86/kernel/kvmclock.c:85) > [ 829.539386] ? sched_clock (./arch/x86/include/asm/paravirt.h:192 arch/x86/kernel/tsc.c:304) > [ 829.539392] ? sched_clock_local (kernel/sched/clock.c:202) > [ 829.539399] numa_migrate_preferred (kernel/sched/fair.c:1539) > [ 829.539404] ? sched_clock_local (kernel/sched/clock.c:202) > [ 829.539411] task_numa_fault (kernel/sched/fair.c:2073) > [ 829.539417] ? sched_clock_cpu (kernel/sched/clock.c:311) > [ 829.539429] ? debug_smp_processor_id (lib/smp_processor_id.c:57) > [ 829.539438] ? get_lock_stats (kernel/locking/lockdep.c:249) > [ 829.539446] ? get_parent_ip (kernel/sched/core.c:2588) > [ 829.539461] handle_mm_fault (mm/memory.c:3187 mm/memory.c:3233 mm/memory.c:3346 mm/memory.c:3375) > [ 829.539466] ? find_vma (mm/mmap.c:2048) > [ 829.539477] __do_page_fault (arch/x86/mm/fault.c:1246) > [ 829.539485] ? context_tracking_user_exit (kernel/context_tracking.c:144) > [ 829.539491] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) > [ 829.539498] ? trace_hardirqs_off_caller (kernel/locking/lockdep.c:2640 (discriminator 8)) > [ 829.539505] trace_do_page_fault (arch/x86/mm/fault.c:1329 include/linux/jump_label.h:114 include/linux/context_tracking_state.h:27 include/linux/context_tracking.h:45 arch/x86/mm/fault.c:1330) > [ 829.539510] do_async_page_fault (arch/x86/kernel/kvm.c:280) > [ 829.539516] async_page_fault (arch/x86/kernel/entry_64.S:1301) The bellow is equal to the patch suggested by Peter. The only thing, I'm doubt, is about the comparison of cpus instead of nids. Should task_numa_compare() be able to be called with src_nid == dst_nid like this may happens now?! Maybe better, we should change task_numa_migrate() and check for env.dst_nid != env.src.nid. diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 826fdf3..c18129e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1380,6 +1380,8 @@ static void task_numa_find_cpu(struct task_numa_env *env, /* Skip this CPU if the source task cannot migrate */ if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p))) continue; + if (cpu == env->src_cpu) + continue; env->dst_cpu = cpu; task_numa_compare(env, taskimp, groupimp); -- 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/