From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10B8AC77B75 for ; Thu, 20 Apr 2023 03:00:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233710AbjDTDAB (ORCPT ); Wed, 19 Apr 2023 23:00:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233065AbjDTC77 (ORCPT ); Wed, 19 Apr 2023 22:59:59 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95BF11FE5; Wed, 19 Apr 2023 19:59:57 -0700 (PDT) Received: from dggpemm500001.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4Q22Rq2rsnz8xC7; Thu, 20 Apr 2023 10:59:03 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Thu, 20 Apr 2023 10:59:54 +0800 Message-ID: <6dc1b117-020e-be9e-7e5e-a349ffb7d00a@huawei.com> Date: Thu, 20 Apr 2023 10:59:54 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2] mm: hwpoison: coredump: support recovery from dump_user_range() Content-Language: en-US To: Jane Chu , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Thomas Gleixner CC: Alexander Viro , Christian Brauner , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Andrew Morton , Miaohe Lin , "linux-kernel@vger.kernel.org" , Tong Tiangen , Jens Axboe References: <20230417045323.11054-1-wangkefeng.wang@huawei.com> <20230418031243.GA2845864@hori.linux.bs1.fc.nec.co.jp> <54d761bb-1bcc-21a2-6b53-9d797a3c076b@huawei.com> <20230419072557.GA2926483@hori.linux.bs1.fc.nec.co.jp> <9fa67780-c48f-4675-731b-4e9a25cd29a0@huawei.com> <7d0c38a9-ed2a-a221-0c67-4a2f3945d48b@oracle.com> From: Kefeng Wang In-Reply-To: <7d0c38a9-ed2a-a221-0c67-4a2f3945d48b@oracle.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/20 10:03, Jane Chu wrote: > > On 4/19/2023 5:03 AM, Kefeng Wang wrote: >> >> >> On 2023/4/19 15:25, HORIGUCHI NAOYA(堀口 直也) wrote: >>> On Tue, Apr 18, 2023 at 05:45:06PM +0800, Kefeng Wang wrote: >>>> >>>> ... >>>>>> @@ -371,6 +372,14 @@ size_t _copy_mc_to_iter(const void *addr, >>>>>> size_t bytes, struct iov_iter *i) >>>>>>    EXPORT_SYMBOL_GPL(_copy_mc_to_iter); >>>>>>    #endif /* CONFIG_ARCH_HAS_COPY_MC */ >>>>>> +static void *memcpy_from_iter(struct iov_iter *i, void *to, const >>>>>> void *from, >>>>>> +                 size_t size) >>>>>> +{ >>>>>> +    if (iov_iter_is_copy_mc(i)) >>>>>> +        return (void *)copy_mc_to_kernel(to, from, size); >>>>> >>>>> Is it helpful to call memory_failure_queue() if copy_mc_to_kernel() >>>>> fails >>>>> due to a memory error? >>>> >>>> For dump_user_range(), the task is dying, if copy incomplete size, the >>>> coredump will fail and task will exit, also memory_failure will >>>> be called by kill_me_maybe(), >>>> >>>>   CPU: 0 PID: 1418 Comm: test Tainted: G   M               6.3.0-rc5 >>>> #29 >>>>   Call Trace: >>>>    >>>>    dump_stack_lvl+0x37/0x50 >>>>    memory_failure+0x51/0x970 >>>>    kill_me_maybe+0x5b/0xc0 >>>>    task_work_run+0x5a/0x90 >>>>    exit_to_user_mode_prepare+0x194/0x1a0 >>>>    irqentry_exit_to_user_mode+0x9/0x30 >>>>    noist_exc_machine_check+0x40/0x80 >>>>    asm_exc_machine_check+0x33/0x40 >>> >>> Is this call trace printed out when copy_mc_to_kernel() failed by >>> finding >>> a memory error (or in some testcase using error injection)? >> >> I add dump_stack() into memory_failure() to check whether the poisoned >> memory is called or not, and the call trace shows it do call >> memory_failure()， but I get confused when do the test. >> >>> In my understanding, an MCE should not be triggered when MC-safe copy >>> tries >>> to access to a memory error.  So I feel that we might be talking about >>> different scenarios. >>> >>> When I questioned previously, I thought about the following scenario: >>> >>>    - a process terminates abnormally for any reason like segmentation >>> fault, >>>    - then, kernel tries to create a coredump, >>>    - during this, the copying routine accesses to corrupted page to >>> read. >>> >> Yes, we tested like your described, >> >> 1) inject memory error into a process >> 2) send a SIGABT/SIGBUS to process to trigger the coredump >> >> Without patch, the system panic, and with patch only process exits. >> >>> In this case the corrupted page should not be handled by >>> memory_failure() >>> yet (because otherwise properly handled hwpoisoned page should be >>> ignored >>> by coredump process).  The coredump process would exit with failure with >>> your patch, but then, the corrupted page is still left unhandled and can >>> be reused, so any other thread can easily access to it again. >> >> As shown above, the corrupted page will be handled by >> memory_failure(), but what I'm wondering, >> 1) memory_failure() is not always called >> 2) look at the above call trace, it looks like from asynchronous >>     interrupt, not from synchronous exception, right? >> >>> >>> You can find a few other places (like __wp_page_copy_user and >>> ksm_might_need_to_copy) >>> to call memory_failure_queue() to cope with such unhandled error pages. >>> So does memcpy_from_iter() do the same? >> >> I add some debug print in do_machine_check() on x86: >> >> 1) COW, >>    m.kflags: MCE_IN_KERNEL_RECOV >>    fixup_type: EX_TYPE_DEFAULT_MCE_SAFE >> >>    CPU: 11 PID: 2038 Comm: einj_mem_uc >>    Call Trace: >>     <#MC> >>     dump_stack_lvl+0x37/0x50 >>     do_machine_check+0x7ad/0x840 >>     exc_machine_check+0x5a/0x90 >>     asm_exc_machine_check+0x1e/0x40 >>    RIP: 0010:copy_mc_fragile+0x35/0x62 >> >>    if (m.kflags & MCE_IN_KERNEL_RECOV) { >>            if (!fixup_exception(regs, X86_TRAP_MC, 0, 0)) >>                    mce_panic("Failed kernel mode recovery", &m, msg); >>    } >> >>    if (m.kflags & MCE_IN_KERNEL_COPYIN) >>            queue_task_work(&m, msg, kill_me_never); >> >> There is no memory_failure() called when >> EX_TYPE_DEFAULT_MCE_SAFE, also EX_TYPE_FAULT_MCE_SAFE too, >> so we manually add a memory_failure_queue() to handle with >> the poisoned page. >> >> 2） Coredump,  nothing print about m.kflags and fixup_type, >> with above check, add a memory_failure_queue() or memory_failure() seems >> to be needed for memcpy_from_iter(), but it is totally different from >> the COW scenario >> >> >> Another question, other copy_mc_to_kernel() callers, eg, >> nvdimm/dm-writecache/dax, there are not call memory_failure_queue(), >> should they need a memory_failure_queue(), if so, why not add it into >> do_machine_check() ? > What I mean is that EX_TYPE_DEFAULT_MCE_SAFE/EX_TYPE_FAULT_MCE_SAFE is designed to identify fixups which allow in kernel #MC recovery, that is, the caller of copy_mc_to_kernel() must know the source is a user address, so we could add a MCE_IN_KERNEL_COPYIN fro the MCE_SAFE type. diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c index c4477162c07d..63e94484c5d6 100644 --- a/arch/x86/kernel/cpu/mce/severity.c +++ b/arch/x86/kernel/cpu/mce/severity.c @@ -293,12 +293,11 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs) case EX_TYPE_COPY: if (!copy_user) return IN_KERNEL; - m->kflags |= MCE_IN_KERNEL_COPYIN; fallthrough; case EX_TYPE_FAULT_MCE_SAFE: case EX_TYPE_DEFAULT_MCE_SAFE: - m->kflags |= MCE_IN_KERNEL_RECOV; + m->kflags |= MCE_IN_KERNEL_RECOV | MCE_IN_KERNEL_COPYIN; return IN_KERNEL_RECOV; default: then we could drop memory_failure_queue(pfn, flags) from cow/ksm copy, or every Machine Check safe memory copy will need a memory_failure_xx() call. +Thomas，who add the two types, could you share some comments about this,thanks. > In the dax case, if the source address is poisoned, and we do follow up > with memory_failure_queue(pfn, flags), what should the value of the > 'flags' be ? I think flags = 0 is enough to for all copy_mc_xxx to isolate the poisoned page. Thanks.