From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail02.groups.io (mail02.groups.io [66.175.222.108]) by spool.mail.gandi.net (Postfix) with ESMTPS id 25AB3AC1098 for ; Wed, 18 Oct 2023 12:20:33 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=w4DNl2OXOqc6gEWG6ta7AeP2M8ta4JtJcg1WQH/WQZI=; c=relaxed/simple; d=groups.io; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From:In-Reply-To:Precedence:List-Subscribe:List-Help:Sender:List-Id:Mailing-List:Delivered-To:Reply-To:List-Unsubscribe-Post:List-Unsubscribe:Content-Language:Content-Type:Content-Transfer-Encoding; s=20140610; t=1697631632; v=1; b=CX4VTcyGvH9iCvOA/lIaFwzHWU31oE2Vr9fkZSvsVGD1uIm4AyKNRzkeiSqPlz+utc7VEqB3 zB2oOSBtEEZ3jS5fRSlUsfi7UhZta61YMT2v5YmPDNamLvFJr98CIO65quxpd+1CxOdHrNWGsPM IFVk6CyXjKV98kQ50OGuMXCU= X-Received: by 127.0.0.2 with SMTP id htQyYY7687511x2GGzD72GR1; Wed, 18 Oct 2023 05:20:32 -0700 X-Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by mx.groups.io with SMTP id smtpd.web10.280272.1697631632086551071 for ; Wed, 18 Oct 2023 05:20:32 -0700 X-Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-464-a27_OKVOPfegKf8P87jKOA-1; Wed, 18 Oct 2023 08:20:30 -0400 X-MC-Unique: a27_OKVOPfegKf8P87jKOA-1 X-Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3BB89380450F; Wed, 18 Oct 2023 12:20:29 +0000 (UTC) X-Received: from [10.39.192.202] (unknown [10.39.192.202]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6258A8C1; Wed, 18 Oct 2023 12:20:27 +0000 (UTC) Message-ID: <0bc96936-0267-ef0c-a0bd-c36c5918af67@redhat.com> Date: Wed, 18 Oct 2023 14:20:25 +0200 MIME-Version: 1.0 Subject: Re: [edk2-devel] [PATCH 1/1] OvmfPkg/VirtioFsDxe: fix SimpleFileOpen To: Pedro Falcato , devel@edk2.groups.io Cc: Gerd Hoffmann , Jordan Justen , Ard Biesheuvel , Oliver Steffen , Jiewen Yao , =?UTF-8?Q?Marvin_H=c3=a4user?= References: <20231018103328.91093-1-kraxel@redhat.com> From: "Laszlo Ersek" In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Precedence: Bulk List-Subscribe: List-Help: Sender: devel@edk2.groups.io List-Id: Mailing-List: list devel@edk2.groups.io; contact devel+owner@edk2.groups.io Reply-To: devel@edk2.groups.io,lersek@redhat.com List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: X-Gm-Message-State: bQHK0kR2ZQwtM4sO7sbYtLTJx7686176AA= Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=CX4VTcyG; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=redhat.com (policy=none); spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 66.175.222.108 as permitted sender) smtp.mailfrom=bounce@groups.io On 10/18/23 13:33, Pedro Falcato wrote: > On Wed, Oct 18, 2023 at 12:20 PM Laszlo Ersek wrote: >> >> On 10/18/23 12:33, Gerd Hoffmann wrote: >>> VirtiofsDxe throws an error in case the caller tries to open a file or >>> directory using an handle with is not a directory, claiming that opening >>> something relative to a file does not make sense. >>> >>> The claim is correct, but the code throws errors for both relative and >>> absolute paths. Add a check to fix that. >>> >>> Signed-off-by: Gerd Hoffmann >>> --- >>> OvmfPkg/VirtioFsDxe/SimpleFsOpen.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c b/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >>> index a13d4f6a1e2d..1729ea2f5cf2 100644 >>> --- a/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >>> +++ b/OvmfPkg/VirtioFsDxe/SimpleFsOpen.c >>> @@ -397,7 +397,7 @@ VirtioFsSimpleFileOpen ( >>> // it cannot be implemented consistently with how a file is referred to >>> // relative to a directory). >>> // >>> - if (!VirtioFsFile->IsDirectory) { >>> + if (!VirtioFsFile->IsDirectory && FileName[0] != '\\') { >>> DEBUG (( >>> DEBUG_ERROR, >>> ("%a: Label=\"%s\" CanonicalPathname=\"%a\" FileName=\"%s\": " >> >> It's nice to see this topic pop up on edk2-devel; apparently you started >> testing shim on top of virtio-fs. :) >> >> I have had the following patch in my local repo, on a separate branch, >> since April this year: >> >>> commit cb4a6d1664ea6cabd14d2af0e5d9abb114973870 >>> Author: Laszlo Ersek >>> Date: Sat Apr 8 22:50:50 2023 +0200 >>> >>> OvmfPkg/VirtioFsDxe: tolerate opening an abs. pathname rel. to a reg. file >>> >>> Referring to a file relative to a regular file makes no sense (or at least >>> it cannot be implemented consistently with how a file is referred to >>> relative to a directory). VirtioFsSimpleFileOpen() has enforced this >>> strictly since the beginning, and a few months ago I reported USWG Mantis >>> ticket #2367 [1] too, for clearing up the related confusion in the UEFI >>> spec. >>> >>> Unfortunately, the shim boot loader contains such a bug [2] [3]. I don't >>> believe the shim bug is ever going to be fixed. We can however relax the >>> check in VirtioFsSimpleFileOpen() a bit: if the pathname that's being >>> opened relative to a regular file is absolute, then the base file is going >>> to be ignored anyway, so we can let the caller's bug slide. This happens >>> to make shim work. >>> >>> Why this matters: UEFI-bootable Linux installer ISOs tend to come with >>> shim and grub in the embedded (ElTorito) FAT image (ESP). Sometimes you >>> want to build upstream shim/grub binaries, but boot the same ISO >>> otherwise. The fastest way for overriding the ESP for this purpose is to >>> copy its original contents to a virtio filesystem, then overwrite the shim >>> and grub binaries from the host side. Note that this is different from >>> direct-booting a kernel (via fw_cfg); the point is to check whether the >>> just-built shim and grub are able to boot the rest of the ISO. >>> >>> [1] https://mantis.uefi.org/mantis/view.php?id=2367 > > What does the mantis ticket say/conclude? Yay for private bug trackers > that need corporate buy-in... I posted patches for the UEFI spec. (In two formats -- as a pull request to the locked-down repository on github.com, and as attachments.) Kevin W Shaw started reviewing my patches, but he seemed to misunderstand the git patch format in general; so I commented on that, but then the thread petered out. So it's stuck at the moment. I guess I could try to join USWG meetings / calls and champion the issue there, but I had not had time for that for a decade, and I don't have it now. I'd hope we could communicate asynchronously, via bug trackers... > > FWIW, Ext4Dxe does > [...] > > if (!Ext4FileIsDir (Current)) { > return EFI_INVALID_PARAMETER; > } > > // If the path starts with a backslash, we treat the root directory > as the base directory > if (FileName[0] == L'\\') { > FileName++; > Current = Partition->Root; > } > > so if shim/other important UEFI apps have a bug, I may need to fix > this as well... > I vaguely remember that I looked up both Ext4Dxe and EnhancedFatDxe regarding this question, but I don't remember what my take-away was at the time. :) Clearly, EnhancedFatDxe must be tolerant of this bug, otherwise shim would never boot off of "normal" (i.e., FAT32) ESPs. Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. 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