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[2604:1380:45e3:2400::1]) by mx.google.com with ESMTPS id t12-20020a63534c000000b005ce08b3fe78si1415093pgl.126.2023.12.23.20.46.18 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 Dec 2023 20:46:19 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-10633-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=ZMIZ8lqm; spf=pass (google.com: domain of linux-kernel+bounces-10633-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) smtp.mailfrom="linux-kernel+bounces-10633-linux.lists.archive=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id B89DD2827DF for ; Sun, 24 Dec 2023 04:46:18 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D6B98ED2; Sun, 24 Dec 2023 04:46:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZMIZ8lqm" X-Original-To: linux-kernel@vger.kernel.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E0B6EBC for ; Sun, 24 Dec 2023 04:46:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703393169; 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=NfIP5VGXxX0Vbo7RIsC7FRwPJeV44ad3sg3nU9VzDsE=; b=ZMIZ8lqmpkEFoMvCnVC63iSllkbJQGbiHTi7TwVGgDhbWvOLcm7mwaGN7u4DpTPicqtoaV p3ERBRp6ifn2GYd2wR8PLODLsDAEhAq/LYkVP6hNGSY14/AQR6cR3bUNSUTSWiu9uV9o6O quox1CY0/HIQRABSD0TnIxuA9DnYgCo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-310-k0nEAYs9O-mOBrNey4ZvAw-1; Sat, 23 Dec 2023 23:46:05 -0500 X-MC-Unique: k0nEAYs9O-mOBrNey4ZvAw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 394938339B8; Sun, 24 Dec 2023 04:46:05 +0000 (UTC) Received: from localhost (unknown [10.72.116.38]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 864A3C15968; Sun, 24 Dec 2023 04:46:03 +0000 (UTC) Date: Sun, 24 Dec 2023 12:46:00 +0800 From: Baoquan He To: fuqiang wang Cc: Vivek Goyal , Dave Young , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] x86/kexec: fix potential cmem->ranges out of bounds Message-ID: References: <20231222121855.148215-1-fuqiang.wang@easystack.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 On 12/22/23 at 09:29pm, Baoquan He wrote: > On 12/22/23 at 08:18pm, fuqiang wang wrote: > > In memmap_exclude_ranges(), there will exclude elfheader from > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > elfheader will be excluded from crashk_res. OR > it will exclude elfheader from crashk_res. > > > crashk_res. In the current x86 architecture code, the elfheader is > > always allocated at crashk_res.start. It seems that there won't be a > > split a new range. But it depends on the allocation position of > ~~~~~~~~~~~~~~~~~~ > It seems that there won't be a new split range. > > elfheader in crashk_res. To avoid potential out of bounds in future, add > > a extra slot. > > > > The similar issue also exists in fill_up_crash_elf_data(). The range to > > be excluded is [0, 1M], start (0) is special and will not appear in the > > middle of existing cmem->ranges[]. But in order to lest the low 1M could > ~~~~~~~~~~~~~~~~ > in case > > be changed in the future, add a extra slot too. > > > > Previously discussed link: > > [1] https://lore.kernel.org/kexec/ZXk2oBf%2FT1Ul6o0c@MiWiFi-R3L-srv/ > > [2] https://lore.kernel.org/kexec/273284e8-7680-4f5f-8065-c5d780987e59@easystack.cn/ > > [3] https://lore.kernel.org/kexec/ZYQ6O%2F57sHAPxTHm@MiWiFi-R3L-srv/ > > > > Signed-off-by: fuqiang wang > > --- > > arch/x86/kernel/crash.c | 21 +++++++++++++++++++-- > > 1 file changed, 19 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c > > index c92d88680dbf..97d33a6fc4fb 100644 > > --- a/arch/x86/kernel/crash.c > > +++ b/arch/x86/kernel/crash.c > > @@ -149,8 +149,18 @@ static struct crash_mem *fill_up_crash_elf_data(void) > > /* > > * Exclusion of crash region and/or crashk_low_res may cause > > * another range split. So add extra two slots here. > > + * > > + * Exclusion of low 1M may not cause another range split, because the > > + * range of exclude is [0, 1M] and the condition for splitting a new > > + * region is that the start, end parameters are both in a certain > > + * existing region in cmem and cannot be equal to existing region's > > + * start or end. Obviously, the start of [0, 1M] cannot meet this > > + * condition. > > + * > > + * But in order to lest the low 1M could be changed in the future, > > + * (e.g. [stare, 1M]), add a extra slot. Rethink about this, seems above code comment is fine to be kept, and the same feeling about the elfheader region split from crashk_res. So, other than the patch log concerns, this patch looks good to me. Let's see if other people has concern about the newly added comments. > > Sometime, too much is as bad as too little. I feel below words are > enough to state three regions are gonna be excluded, and may cause > another split (may not cause). The code comment plus commit log can help > people know why they are needed. > > * Exclusion of low1M, crashk_res and/or crashk_low_res may cause > * another range split. So add extra three slots here. > > > */ > > - nr_ranges += 2; > > + nr_ranges += 3; > > cmem = vzalloc(struct_size(cmem, ranges, nr_ranges)); > > if (!cmem) > > return NULL; > > @@ -282,9 +292,16 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params) > > struct crash_memmap_data cmd; > > struct crash_mem *cmem; > > > > - cmem = vzalloc(struct_size(cmem, ranges, 1)); > > + /* > > + * In the current x86 architecture code, the elfheader is always > > + * allocated at crashk_res.start. But it depends on the allocation > > + * position of elfheader in crashk_res. To avoid potential out of > > + * bounds in future, add a extra slot. > > + */ > > Ditto. > > + /* > + * Elfheader gonna be excluded from crashk_res, to avoid potential > + * out of bounds, add one extra slot. > + */ > > > + cmem = vzalloc(struct_size(cmem, ranges, 2)); > > if (!cmem) > > return -ENOMEM; > > + cmem->max_nr_ranges = 2; > > > > memset(&cmd, 0, sizeof(struct crash_memmap_data)); > > cmd.params = params; > > -- > > 2.42.0 > > >