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=-0.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 AE268C2BB86 for ; Thu, 9 Apr 2020 14:39:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 82B6F2078E for ; Thu, 9 Apr 2020 14:39:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RFiloriP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727794AbgDIOjO (ORCPT ); Thu, 9 Apr 2020 10:39:14 -0400 Received: from mail-qv1-f67.google.com ([209.85.219.67]:37699 "EHLO mail-qv1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727368AbgDIOjO (ORCPT ); Thu, 9 Apr 2020 10:39:14 -0400 Received: by mail-qv1-f67.google.com with SMTP id n1so5584722qvz.4; Thu, 09 Apr 2020 07:39:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=V0peUcS4xyy6xzU2lui7tASWzqbXgbJ8PVWPkgOy87s=; b=RFiloriPPxNl0UwUwYFNvjkQ9B8zNeV1F2WqXq8W32IOtZkfIxpqRPoQrEYtCYyGUP ygUK3mwr7qTV3R6x8c7ilNyb/V1tKjGSoxfVd5uk1mp91hKB4e6iTYzJ0ZlvioPmNVRM Ei/Cs1woOrhsRMK6jreFMlLIw/OEfu28s/R4mdDneKg4oXIx66ZB1+lW6q6g5KBnrSt8 E+BwdceRHn3cKMcDs3BDS+PXeCbeUep+wrB699VInBE+9LiXh2MXQF09JDQ3VFU5bdXr LdESYtYUavSLYVJPT+NWFqzgpDOYfKYoxuG69prZloX3HDfMBk3GUU5Eh99dRkgVMVmv Ih4A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:date:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=V0peUcS4xyy6xzU2lui7tASWzqbXgbJ8PVWPkgOy87s=; b=XsfQ5aIFojdZtSPqc1gD/XTFKj4GEkEZf7m2O7U4/oJyA7jtzvv3XIs5YoMxn1x51o b53wWIPyEyn0T5nxHHmXfpo+PHJXXPVkdIMVQA1GJx2wLpLYbMW5yhuwUdPtWsHWIVh+ D4Komwmrpv059FeJFJcVSMj/JiN5pFLcv1XG11hcmNwATcrHpj++BUx2GW9PVlD0uGrv Fu1Q1a+3vCZVxkXFzru48R893nfeupzCKnyxbN1if4znoWRrQrNYOlEZnt0S9o9buzN9 DrCfKiq7uALw//JizA1Lu/X5h1EJADvH9Jxw7nueTWkM+8W9HKZZUKRIZUicdjb/4F57 xuCA== X-Gm-Message-State: AGi0PubLwm8Nzo1o86rrKi9TkltyZZFMvm1RZgDcfV9cfdSImvcYLZ4Z kRQPUKzcJmCBZLjQpe2QNvk= X-Google-Smtp-Source: APiQypKR9/XpDamJYVfxyRTxLwmb+HIiAdic1PwWBGZ+2jeo+4tSTFUem5fLxgYZEwsb3kHKg+JU5Q== X-Received: by 2002:a0c:9aee:: with SMTP id k46mr307996qvf.7.1586443153294; Thu, 09 Apr 2020 07:39:13 -0700 (PDT) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id d24sm20629143qkl.8.2020.04.09.07.39.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2020 07:39:12 -0700 (PDT) From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Thu, 9 Apr 2020 10:39:10 -0400 To: Ard Biesheuvel Cc: Dave Young , pjones@redhat.com, daniel.kiper@oracle.com, Leif Lindholm , Arvind Sankar , Borislav Petkov , Sergey Shatunov , hpa@zytor.com, Linux Kernel Mailing List , mingo@redhat.com, Thomas Gleixner , x86@kernel.org, linux-efi , initramfs@vger.kernel.org, Donovan Tremura , Harald Hoyer Subject: Re: [PATCH 1/2] efi/x86: Move efi stub globals from .bss to .data Message-ID: <20200409143910.GA727557@rani.riverdale.lan> References: <20200406180614.429454-1-nivedita@alum.mit.edu> <20200408074334.GA21886@dhcp-128-65.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 08, 2020 at 09:49:15AM +0200, Ard Biesheuvel wrote: > (add Peter, Leif and Daniel) > > On Wed, 8 Apr 2020 at 09:43, Dave Young wrote: > > > > On 04/06/20 at 02:06pm, Arvind Sankar wrote: > > > Commit > > > > > > 3ee372ccce4d ("x86/boot/compressed/64: Remove .bss/.pgtable from > > > bzImage") > > > > > > removed the .bss section from the bzImage. > > > > > > However, while a PE loader is required to zero-initialize the .bss > > > section before calling the PE entry point, the EFI handover protocol > > > does not currently document any requirement that .bss be initialized by > > > the bootloader prior to calling the handover entry. > > > > > > When systemd-boot is used to boot a unified kernel image [1], the image > > > is constructed by embedding the bzImage as a .linux section in a PE > > > executable that contains a small stub loader from systemd together with > > > additional sections and potentially an initrd. As the .bss section > > > within the bzImage is no longer explicitly present as part of the file, > > > it is not initialized before calling the EFI handover entry. > > > Furthermore, as the size of the embedded .linux section is only the size > > > of the bzImage file itself, the .bss section's memory may not even have > > > been allocated. > > > > I did not follow up the old report, maybe I missed something. But not > > sure why only systemd-boot is mentioned here. I also have similar issue > > with early efi failure. With these two patches applied, it works well > > then. > > > > BTW, I use Fedora 31 + Grub2 > > > > OK, so I take it this means that GRUB's PE/COFF loader does not > zero-initialize BSS either? Does it honor the image size in memory if > it exceeds the file size? Dave, that comment was because the previous report was for systemd-boot stub. Ard, should I revise the commit message to make it clear it's not restricted to systemd-boot but anything using handover entry may be affected? Maybe just a "for example, when systemd-boot..." and then a line to say grub2 with the EFI stub patches is also impacted? https://src.fedoraproject.org/rpms/grub2/blob/f31/f/0001-Add-support-for-Linux-EFI-stub-loading.patch#_743 + kernel_mem = grub_efi_allocate_pages_max(lh.pref_address, + BYTES_TO_PAGES(lh.init_size)); Looking at this, grub does allocate init_size for the image, but it doesn't zero it out. This call also looks wrong to me though. It allocates at max address of pref_address, which, if it succeeds, will guarantee that the kernel gets loaded entirely below pref_address == LOAD_PHYSICAL_ADDR. In native mode, if it weren't for the EFI stub copying the kernel again, this would cause the startup code to relocate the kernel into unallocated memory. On a mixed-mode boot, this would cause the early page tables setup prior to transitioning to 64-bit mode to be in unallocated memory and potentially get clobbered by the EFI stub. The first try to allocate pref_address should be calling grub_efi_allocate_fixed instead.