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 CA92DC678D4 for ; Tue, 17 Jan 2023 16:56:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230202AbjAQQ4d (ORCPT ); Tue, 17 Jan 2023 11:56:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33768 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231180AbjAQQ4a (ORCPT ); Tue, 17 Jan 2023 11:56:30 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 631D6442C3; Tue, 17 Jan 2023 08:56:29 -0800 (PST) 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 sin.source.kernel.org (Postfix) with ESMTPS id A62D6CE1901; Tue, 17 Jan 2023 16:56:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4217DC433EF; Tue, 17 Jan 2023 16:56:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673974586; bh=awCNWH6g7iC9TQ3N6frBiPrp8RzZqPKgyt/xKy5+Jiw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Pj0stw7n9lbjyENNQ49z3XXqSi6KW8hjJYhTOhOEG18HH4QeclSR/dCoed+6xqQ6z cce5s7CFNM8lWJNW68bDzuW9sDaXpSGi/eSHWROOL3AKQaWPhkeZy2OKUEYCcHoiCh ZFis46o88QvIFxhytSD2zIHRUPNVki625AEO4k46WGwRpXqmMYY9QSXnbe7lkC3Ek7 vBJp/4an4PKB3pOKqqTRrF6UqYSACaunit1bJDEUciDG0/p4WsjFpOet7KrleoCek9 3FiHywENR3rlfqHNQ+ToO9eX6/q2RKyy2mdDRgCW3fhsougclBTebEM+GQdvuRBOPL qUkACBdRK66Vw== Date: Tue, 17 Jan 2023 16:56:19 +0000 From: Lee Jones To: Greg KH Cc: Ard Biesheuvel , Mark Rutland , stable@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, will@kernel.org, catalin.marinas@arm.com, Sami Tolvanen , Kees Cook Subject: Re: [PATCH 1/2] arm64: efi: Execute runtime services from a dedicated stack Message-ID: References: <20221205201210.463781-1-ardb@kernel.org> <20221205201210.463781-2-ardb@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, 05 Jan 2023, Greg KH wrote: > On Wed, Jan 04, 2023 at 05:32:18PM +0100, Ard Biesheuvel wrote: > > On Wed, 4 Jan 2023 at 17:30, Mark Rutland wrote: > > > > > > On Wed, Jan 04, 2023 at 05:15:34PM +0100, Ard Biesheuvel wrote: > > > > On Wed, 4 Jan 2023 at 17:13, Mark Rutland wrote: > > > > > > > > > > On Wed, Jan 04, 2023 at 02:56:19PM +0100, Ard Biesheuvel wrote: > > > > > > On Wed, 4 Jan 2023 at 11:40, Lee Jones wrote: > > > > > > > > > > > > > > On Mon, 05 Dec 2022, Ard Biesheuvel wrote: > > > > > > > > > > > > > > > With the introduction of PRMT in the ACPI subsystem, the EFI rts > > > > > > > > workqueue is no longer the only caller of efi_call_virt_pointer() in the > > > > > > > > kernel. This means the EFI runtime services lock is no longer sufficient > > > > > > > > to manage concurrent calls into firmware, but also that firmware calls > > > > > > > > may occur that are not marshalled via the workqueue mechanism, but > > > > > > > > originate directly from the caller context. > > > > > > > > > > > > > > > > For added robustness, and to ensure that the runtime services have 8 KiB > > > > > > > > of stack space available as per the EFI spec, introduce a spinlock > > > > > > > > protected EFI runtime stack of 8 KiB, where the spinlock also ensures > > > > > > > > serialization between the EFI rts workqueue (which itself serializes EFI > > > > > > > > runtime calls) and other callers of efi_call_virt_pointer(). > > > > > > > > > > > > > > > > While at it, use the stack pivot to avoid reloading the shadow call > > > > > > > > stack pointer from the ordinary stack, as doing so could produce a > > > > > > > > gadget to defeat it. > > > > > > > > > > > > > > > > Signed-off-by: Ard Biesheuvel > > > > > > > > --- > > > > > > > > arch/arm64/include/asm/efi.h | 3 +++ > > > > > > > > arch/arm64/kernel/efi-rt-wrapper.S | 13 +++++++++- > > > > > > > > arch/arm64/kernel/efi.c | 25 ++++++++++++++++++++ > > > > > > > > 3 files changed, 40 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > Could we have this in Stable please? > > > > > > > > > > > > > > Upstream commit: ff7a167961d1b ("arm64: efi: Execute runtime services from a dedicated stack") > > > > > > > > > > > > > > Ard, do we need Patch 2 as well, or can this be applied on its own? > > > > > > > > > > > > > > > > > > > Thanks for the reminder. > > > > > > > > > > > > Only patch #1 is needed. It should be applied to v5.10 and later. > > > > > > > > > > Hold on, why did this go into mainline when I had an outstanding comment w.r.t. > > > > > the stack unwinder? > > > > > > > > > > From your last reply to me there I was expecting a respin with that fixed. > > > > > > > > > > > > > Apologies for the confusion. > > > > > > > > I have a patch for this queued up, but AIUI, that cannot be merged all > > > > the way back to v5.10, so these need to remain separate changes in any > > > > case. > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=c2530a04a73e6b75ed71ed14d09d7b42d6300013 > > > > > > Ah, ok, thanks for the pointer! > > > > > > I'm a little uneasy here, still. > > > > > > By backporting this we're also backporting the new breakage of the stack > > > unwinder, and the minimal change for backports would be to add the lock and not > > > the new stack (which was added for additinoal robustness, not to fix the bug > > > the lock fixes). > > > > > > I do appreciate that the additional stack is likely more useful than the > > > occasional diagnostic output from the kernel, but it does seem like this has > > > traded off one bug for another, and I'm just a little annoyed because I pointed > > > that out before the first pull request was made. > > > > > > I do know that this isn't malicious, and I'm not trying to start a fight, but > > > now we have to consider whether we want/need to backport a stack unwinder fix > > > to account for this, and we hadn't had that discussion before. > > > > > > > In that case, let's drop these backports for the time being, and > > collaborate on a solution that works for all of us. > > > > Greg, could you please drop these again? Thanks. > > Dropped now from all queues, thanks. Now in Mainline as: 18bba1843fc7f efi: rt-wrapper: Add missing include ff7a167961d1b arm64: efi: Execute runtime services from a dedicated stack Would you be kind enough to re-collect them please? Thank you. -- Lee Jones [李琼斯]