From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8BF06606A31C for ; Thu, 12 Nov 2026 16:19:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=eInzyfFZ Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xRXWR-0005B4-RJ; Thu, 12 Nov 2026 11:19:36 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xRXWG-00054h-7R for qemu-devel@nongnu.org; Thu, 12 Nov 2026 11:19:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xRXWE-0004fv-An for qemu-devel@nongnu.org; Thu, 12 Nov 2026 11:19:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1794500361; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Th/dgS5bBEKxxMHxfnZdr/dlaTNnFJXmTSfjd2WpWcs=; b=eInzyfFZXKKgWpTpXmOMRKkkabReTmpUpmPzpJ+I4ABOKP0K6C/x2sZPo1wA2/73zeTcPF WKu5/kPuQtc1jmJWEn71x8orHZNfHly2aDwYFNRyG4Apw2OIBjFNmrT65Q8RA0LWKLQ45O HG/kB+Yk4ThPY93LoqbwVpTYvEkZ3Xg= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-215-KVWNNvn_NpWTKWCPSkmwHw-1; Thu, 12 Nov 2026 11:19:17 -0500 X-MC-Unique: KVWNNvn_NpWTKWCPSkmwHw-1 X-Mimecast-MFC-AGG-ID: KVWNNvn_NpWTKWCPSkmwHw_1794500356 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 919A21956058; Thu, 12 Nov 2026 16:19:16 +0000 (UTC) Received: from redhat.com (unknown [10.44.32.60]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 90B5830000E5; Thu, 12 Nov 2026 16:19:14 +0000 (UTC) Date: Thu, 12 Nov 2026 17:19:12 +0100 From: Kevin Wolf To: Thomas Huth Cc: qemu-devel@nongnu.org, Peter Maydell , Hanna Reitz , qemu-block@nongnu.org, Eric Blake Subject: Re: [PATCH] block/vhdx: Add alignment checks for region tables Message-ID: References: <20261112092201.74651-1-thuth@redhat.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 5 X-Spam_score: 0.5 X-Spam_bar: / X-Spam_report: (0.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-20.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Am 12.11.2026 um 15:48 hat Thomas Huth geschrieben: > Am 12.11.26 um 13:49 schrieb Kevin Wolf: > > Am 12.11.2026 um 10:22 hat Thomas Huth geschrieben: > > > According to the VHDX specification: > > > > > > "The FileOffset and Length fields specify the 64-bit byte offset and 32-bit > > > byte length of the object within the file. The values must be a multiple of > > > 1 MB, and FileOffset must be at least 1 MB." > > > > This requires that the offset (not length) is at least 1 MB... > > > > > Thus let's add a sanity check to avoid that bad things could happen later. > > > > > > Buglink: https://gitlab.com/qemu-project/qemu/-/work_items/3762 > > > Reported-by: Daniel Wade > > > Signed-off-by: Thomas Huth > > > --- > > > v2: Use QEMU_IS_ALIGNED() as suggested by Eric > > > > > > block/vhdx.c | 10 ++++++++++ > > > 1 file changed, 10 insertions(+) > > > > > > diff --git a/block/vhdx.c b/block/vhdx.c > > > index 8013a90a1a4..21270988b5a 100644 > > > --- a/block/vhdx.c > > > +++ b/block/vhdx.c > > > @@ -566,6 +566,16 @@ vhdx_open_region_tables(BlockDriverState *bs, BDRVVHDXState *s) > > > vhdx_region_entry_le_import(&rt_entry); > > > + /* > > > + * According to the VHDX spec, offset and length must be multiple > > > + * of 1 MiB and length must be at least 1 MiB. > > > + */ > > > + if (!QEMU_IS_ALIGNED(rt_entry.file_offset, MiB) || > > > + !QEMU_IS_ALIGNED(rt_entry.length, MiB) || !rt_entry.length) { > > > > ...but the comment and code do the opposite and check only that the > > length is at least 1 MB, leaving FileOffset (which was the actual > > requirement) unchecked. > > D'oh, stupid me! I was apparently sloppy when reading the spec, sorry! > (though a zero length likely also does not make much sense...) Yes, I wouldn't have complained about the extra check for length, but checking the offset seems important. > > > > > > + ret = -EINVAL; > > > + goto fail; > > > + } > > > + > > > /* check for region overlap between these entries, and any > > > * other memory regions in the file */ > > > ret = vhdx_region_check(s, rt_entry.file_offset, rt_entry.length); > > > > I'm also wondering if the check shouldn't be in vhdx_region_check() > > instead, which we're already calling here. > > I considered that, too, but finally decided against it since > vhdx_region_check() seemed rather about overlapping regions... but if you > prefer, I can also move it there. There's a comment at vhdx_region_check() that could use an update then, but the name vhdx_region_check() feels generic enough to me. But this is not a requirement from my side, just a thought I had. If we both had it, maybe that means something, but you decide. Kevin