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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (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 D300FCC6B19 for ; Tue, 13 Oct 2026 20:23:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xGj1R-0005ms-KC; Tue, 13 Oct 2026 16:22:53 -0400 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 1xGj1P-0005mG-Ue for qemu-devel@nongnu.org; Tue, 13 Oct 2026 16:22:51 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xGj1N-00055l-RC for qemu-devel@nongnu.org; Tue, 13 Oct 2026 16:22:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1791922968; 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=YOT+f1zaSuWdUYtO+lrW4iJeMVKSkeCNlIOULsoGjFI=; b=HqYMedqYPjq00THYwGkFaBYBuxXH2+Ns1mUZFtjNEUpWnYCzpk6j/CdJyfX+wmNF/Idvj+ EAFUcyb0VxABMKnOfJ+vKFt4LSwN2OpvlqAOiUPtWsBUpDNFNsYMKNU91Q3s14l016Ji03 jgffMSljeEkZ9lphj4t0myWOpX9HqFw= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-54-6iBb32FtPuy52Q165Cg-2g-1; Tue, 13 Oct 2026 20:22:46 +0000 X-MC-Unique: 6iBb32FtPuy52Q165Cg-2g-1 X-Mimecast-MFC-AGG-ID: 6iBb32FtPuy52Q165Cg-2g_1791922965 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 860C4180AEB4; Tue, 13 Oct 2026 20:22:45 +0000 (UTC) Received: from redhat.com (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9D4ED30001B9; Tue, 13 Oct 2026 20:22:43 +0000 (UTC) Date: Tue, 13 Oct 2026 15:22:41 -0500 From: Eric Blake To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Kevin Wolf , qemu-block@nongnu.org, Hanna Reitz Subject: Re: [PATCH] dmg: avoid out-of-bounds memory load in dmg_read_mish_block() Message-ID: References: <20261013193710.1311621-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261013193710.1311621-1-stefanha@redhat.com> User-Agent: NeoMutt/20260616 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.24, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham 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-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Oct 13, 2026 at 03:37:08PM -0400, Stefan Hajnoczi wrote: > dmg_read_mish_block() loads from memory beyond the end of the buffer > when count is less than 4. > > There is no known security impact here because dmg_read_mish_block() > returns almost immediately without any opportunity to gain control of > execution or cause other damage. A crash will not happen because it's a > 32-bit load from a memory address that was just heap allocated. The > address will be properly aligned and will not span a page of memory. > > Reported-by: router0mail > Fixes: 7aee37b93a4f ("block/dmg: process a buffer instead of reading ints") > Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/4569 > Signed-off-by: Stefan Hajnoczi > --- > block/dmg.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/block/dmg.c b/block/dmg.c > index 5d7d3b8901f..412d4bfc354 100644 > --- a/block/dmg.c > +++ b/block/dmg.c > @@ -226,9 +226,13 @@ static int dmg_read_mish_block(BDRVDMGState *s, DmgHeaderState *ds, > uint64_t in_offset = ds->data_fork_offset; > uint64_t out_offset; > > + if (count < 244) { > + return 0; /* too small, skip silently */ > + } > + > type = buff_read_uint32(buffer, offset); > - /* skip data that is not a valid MISH block (invalid magic or too small) */ > - if (type != 0x6d697368 || count < 244) { > + /* skip data that is not a valid MISH block (invalid magic) */ > + if (type != 0x6d697368) { > /* assume success for now */ > return 0; > } Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. 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