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 9C257C7EE2E for ; Wed, 31 May 2023 01:16:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233760AbjEaBQa (ORCPT ); Tue, 30 May 2023 21:16:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231545AbjEaBQ2 (ORCPT ); Tue, 30 May 2023 21:16:28 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E80FCF3 for ; Tue, 30 May 2023 18:16:25 -0700 (PDT) Received: from dggpemm500006.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4QWB746xqwzqTYs; Wed, 31 May 2023 09:11:44 +0800 (CST) Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Wed, 31 May 2023 09:16:23 +0800 Subject: Re: [PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory() To: Baoquan He CC: Eric Biederman , , , Michael Holzheu , Andrew Morton References: <20230527123439.772-1-thunder.leizhen@huawei.com> <20230527123439.772-2-thunder.leizhen@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: <5232350c-7529-eece-c9cb-8a8bbc83a81a@huawei.com> Date: Wed, 31 May 2023 09:16:22 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/5/31 8:13, Baoquan He wrote: > On 05/27/23 at 08:34pm, Zhen Lei wrote: >> If the value of parameter 'new_size' is in the semi-open and semi-closed >> interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the >> calculation result of ram_res is: >> ram_res->start = crashk_res.end + 1 >> ram_res->end = crashk_res.end > > If the new_size is smaller than KEXEC_CRASH_MEM_ALIGN, does it make > any sense except of testing purpose? Do we need to fail this kind of > shrinking, or just shrink all the left crash memory? We can't give a fixed value, that is, how much crash memory is reserved to ensure that the capture kernel runs. The size of KEXEC_CRASH_MEM_ALIGN is only one page on non-s390 platforms. So, it's better to keep the code simple, and let the user(administrator) shrink the crash memory reasonably. include/linux/kexec.h #define KEXEC_CRASH_MEM_ALIGN PAGE_SIZE > >> The operation of function insert_resource() fails, and ram_res is not >> added to iomem_resource. As a result, the memory of the control block >> ram_res is leaked. >> >> In fact, on all architectures, the start address and size of crashk_res >> are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to >> round up crashk_res.start again. Instead, we should round up 'new_size' >> in advance. >> >> Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()") >> Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size") >> Signed-off-by: Zhen Lei >> --- >> kernel/kexec_core.c | 5 ++--- >> 1 file changed, 2 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c >> index 3d578c6fefee385..22acee18195a591 100644 >> --- a/kernel/kexec_core.c >> +++ b/kernel/kexec_core.c >> @@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long new_size) >> start = crashk_res.start; >> end = crashk_res.end; >> old_size = (end == 0) ? 0 : end - start + 1; >> + new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN); >> if (new_size >= old_size) { >> ret = (new_size == old_size) ? 0 : -EINVAL; >> goto unlock; >> @@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long new_size) >> goto unlock; >> } >> >> - start = roundup(start, KEXEC_CRASH_MEM_ALIGN); >> - end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN); >> - >> + end = start + new_size; >> crash_free_reserved_phys_range(end, crashk_res.end); >> >> if ((start == end) && (crashk_res.parent != NULL)) >> -- >> 2.25.1 >> > > . > -- Regards, Zhen Lei