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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 82FFAC433FE for ; Mon, 7 Nov 2022 20:40:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc: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=y57JR3PwDd/pFnfeZfgRO00QQZratyZQPISgiIS8ELU=; b=PYOqoHXuCCqWvj iIdZ5/Ln0xi8LPZN12rK9b1q1TIO3zvW33ru2go+PeRlxiniKEkJJgOGKBba6NhO7e/9J1Fa2OnkD K1uh55lSaAFTQCztJgM7ELZf0dCw+ukIxUUEuEWB6KkmH8POBh1TCA9QBDnV0FBcOE0SgpinbCkYl B5uM9e8MZAU7YzpA6OAjrGAb3LsA7hqpN5H8fVrwct+IMKHlzmMhlONDKZj/Asns2xVEgw5i8jiSy cIcV+drVmtu/WWTsm0zRUhS4Bq6pOpKlLalJXUz8D9HWNQwjvGGfqd+Lc8jG+RPJfdVOifSBNVNrS n5DvHEKJ5znB825FnWHg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1os8tL-000KoM-UO; Mon, 07 Nov 2022 20:38:48 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1os8tJ-000Knz-Qh for linux-arm-kernel@lists.infradead.org; Mon, 07 Nov 2022 20:38:47 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0231A612F2; Mon, 7 Nov 2022 20:38:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 143AEC433D6; Mon, 7 Nov 2022 20:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667853524; bh=2CPeClRuc5C9p5rm4iumA7wQInldkQ1fN+K3/RZZesM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=XAIeExdHegxfdgJSayGo6D/Q+PPibAbSVVQuB7DO5w4yz0/Ieds2NQtsSUhqA9cHD yhy3jU8YxYU65hSo79MF75cMQgW3tsMVbI/biqZLPWyUvWA8lSTAjKbx++1gNk9QOR 7y4EaXlBiFa8LU/VsulpFus6kPlVM1vzE5wDrleFkYlvXU8BVuKwwEUB+qaIgdE7I2 YvKKR1jWZnfEnoVYNAPXezR+TOXlC/s8y69s9BulCTnP+PQPdLUy2J1IbElLmaZCz5 7hQfSEUOdnfQqapvYpSHutpsLvooOu7mEBgkW3u0RXqIUZDIQm0pAMrlVbG9DCwnQT Ws7apDDtTG5mw== Date: Mon, 7 Nov 2022 12:38:42 -0800 From: Eric Biggers To: Ard Biesheuvel Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Will Deacon , Mark Rutland , Marc Zyngier , "Jason A . Donenfeld" , Kees Cook , Suzuki K Poulose , Adam Langley Subject: Re: [PATCH v2] arm64: Enable data independent timing (DIT) in the kernel Message-ID: References: <20221107172400.1851434-1-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20221107172400.1851434-1-ardb@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221107_123845_924905_68124D78 X-CRM114-Status: GOOD ( 17.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Nov 07, 2022 at 06:24:00PM +0100, Ard Biesheuvel wrote: [...] > > Currently, we have no idea whether or not running privileged code with > DIT disabled on a CPU that implements support for it may result in a > side channel that exposes privileged data to unprivileged user space > processes, so let's be cautious and just enable DIT while running in the > kernel if supported by all CPUs. [...] > > - tweak the commit log so that it doesn't read as if we are fixing an > actual vulnerability I think the above undersells this a bit, as crypto code often relies on instructions being constant-time to prevent leakage of secrets outside the system itself. For example, consider WireGuard, which includes network attackers in its threat model. So it's not just about attacks from userspace processes on the same system. The patch itself looks good to me though -- thanks! - Eric _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel