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 90A4CC77B73 for ; Wed, 31 May 2023 07:31:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234628AbjEaHb5 (ORCPT ); Wed, 31 May 2023 03:31:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234616AbjEaHby (ORCPT ); Wed, 31 May 2023 03:31:54 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C8CE113 for ; Wed, 31 May 2023 00:31:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685518270; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=xgdLJ8iH5oaqpzGT2VDUPLqR1HXU87CsPuv2JR9kJ1k=; b=VmjdWosse65P/mOn3a96FTLFTuPkLeUwB4hQGxZ9j+HLL+sJU745YbgUJzPHyRxd/roZ4p o21yauvIeyivaUUxn7yIvbCQOMf5icE23d0tEPrz6OL7i8eeU3T9EZtAHEm/TfGfzN0iRi PFKoPvYO+AgFXKY63jG1egFl55X23L4= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-379-gbwutGR5OXqtxdF2C-E10A-1; Wed, 31 May 2023 03:31:07 -0400 X-MC-Unique: gbwutGR5OXqtxdF2C-E10A-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B6A101C068CF; Wed, 31 May 2023 07:31:06 +0000 (UTC) Received: from localhost (ovpn-12-54.pek2.redhat.com [10.72.12.54]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DE373492B00; Wed, 31 May 2023 07:31:05 +0000 (UTC) Date: Wed, 31 May 2023 15:31:01 +0800 From: Baoquan He To: "Leizhen (ThunderTown)" Cc: Eric Biederman , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Michael Holzheu , Andrew Morton Subject: Re: [PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory() Message-ID: References: <20230527123439.772-1-thunder.leizhen@huawei.com> <20230527123439.772-2-thunder.leizhen@huawei.com> <5232350c-7529-eece-c9cb-8a8bbc83a81a@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5232350c-7529-eece-c9cb-8a8bbc83a81a@huawei.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/31/23 at 09:16am, Leizhen (ThunderTown) wrote: > > > 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? OK, I misread your log. You are saying the new_size is close to crashk_res.end but has a tiny difference in your example, I thought the new_size is smaller than KEXEC_CRASH_MEM_ALIGN which is just in the opposite direction. Yea, it does have the possibility to waste a ram_res but does nothing even though the chance is very small. Acked-by: Baoquan He > > 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 >