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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C69BC43331 for ; Mon, 30 Mar 2020 11:08:03 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3EB312082D for ; Mon, 30 Mar 2020 11:08:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="JDXfdV75" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3EB312082D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=l9n16Of3duQXmtaq2F5qdfbmKUQXypDGewqbTEXbHsc=; b=JDXfdV751sID8A LAFNyV/Al6nYAF01RTEnqD5T99Y0k3BT48htvCQXLdlAegOosVccl2X/q2ffr94cZe/3qB2t2HJPR EWoj4Z7IIUIHCa+4bYe+ElYlIhP9yUc3EU6jwuX57QcZdz7iXRNxiTIWJSzDSJ/9nvvqPSVEmB9Vd H9SkCjIaAoGYv0CNZ36PQPlxb328dMGf8yNzW8+pkSyAVRsbJDShgAjRC7HWs3K1b3JPTQgAydDnC 473M+WRU8/uhxFjTOxXgBl4lwrBz6QzYmY8jvCAKNBKUuI3wx2iVJ0JP6uuV/3i9j/t5LqYJebi/5 9LZmMega1X3RmRjqkTqQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIsGt-0002fJ-NC; Mon, 30 Mar 2020 11:07:59 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIsGq-0002em-U9 for linux-arm-kernel@lists.infradead.org; Mon, 30 Mar 2020 11:07:58 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DE84D31B; Mon, 30 Mar 2020 04:07:55 -0700 (PDT) Received: from C02TD0UTHF1T.local (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D7A853F52E; Mon, 30 Mar 2020 04:07:53 -0700 (PDT) Date: Mon, 30 Mar 2020 12:07:51 +0100 From: Mark Rutland To: George Spelvin Subject: Re: [RFC PATCH v1 39/50] arm: kexec_file: Avoid temp buffer for RNG seed Message-ID: <20200330110751.GC1309@C02TD0UTHF1T.local> References: <202003281643.02SGhMtr029198@sdf.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <202003281643.02SGhMtr029198@sdf.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200330_040757_020940_080ACCB8 X-CRM114-Status: GOOD ( 17.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Catalin Marinas , linux-kernel@vger.kernel.org, James Morse , Hsin-Yi Wang , Will Deacon , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi George, Nit: s/arm/arm64/ in the title On Tue, Dec 10, 2019 at 10:45:27AM -0500, George Spelvin wrote: > After using get_random_bytes(), you want to wipe the buffer > afterward so the seed remains secret. > > In this case, we can eliminate the temporary buffer entirely. > fdt_setprop_placeholder returns a pointer to the property value > buffer, allowing us to put the random data directy in there without > using a temporary buffer at all. Faster and less stack all in one. > > Signed-off-by: George Spelvin > Cc: Hsin-Yi Wang > Cc: Catalin Marinas > Cc: Will Deacon > Cc: linux-arm-kernel@lists.infradead.org > --- > arch/arm64/kernel/machine_kexec_file.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c > index 7b08bf9499b6b..69e25bb96e3fb 100644 > --- a/arch/arm64/kernel/machine_kexec_file.c > +++ b/arch/arm64/kernel/machine_kexec_file.c > @@ -106,12 +106,12 @@ static int setup_dtb(struct kimage *image, > > /* add rng-seed */ > if (rng_is_initialized()) { > - u8 rng_seed[RNG_SEED_SIZE]; > - get_random_bytes(rng_seed, RNG_SEED_SIZE); > - ret = fdt_setprop(dtb, off, FDT_PROP_RNG_SEED, rng_seed, > - RNG_SEED_SIZE); > + void *rng_seed; > + ret = fdt_setprop_placeholder(dtb, off, FDT_PROP_RNG_SEED, > + RNG_SEED_SIZE, &rng_seed); > if (ret) > goto out; > + get_random_bytes(rng_seed, RNG_SEED_SIZE); This looks sane to me, so FWIW: Acked-by: Mark Rutland Mark. > } else { > pr_notice("RNG is not initialised: omitting \"%s\" property\n", > FDT_PROP_RNG_SEED); > -- > 2.26.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel