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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 C9CBAC76186 for ; Wed, 17 Jul 2019 09:57:55 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9664B20818 for ; Wed, 17 Jul 2019 09:57:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9664B20818 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:55514 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hngh8-0004Nr-U0 for qemu-devel@archiver.kernel.org; Wed, 17 Jul 2019 05:57:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44939) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hnggx-0003wT-BQ for qemu-devel@nongnu.org; Wed, 17 Jul 2019 05:57:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hnggw-0002Kq-5t for qemu-devel@nongnu.org; Wed, 17 Jul 2019 05:57:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43306) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hnggv-0002HY-Tc; Wed, 17 Jul 2019 05:57:42 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id ADC5D307D86F; Wed, 17 Jul 2019 09:57:39 +0000 (UTC) Received: from redhat.com (ovpn-120-247.rdu2.redhat.com [10.10.120.247]) by smtp.corp.redhat.com (Postfix) with SMTP id 30E2A5D9D5; Wed, 17 Jul 2019 09:57:32 +0000 (UTC) Date: Wed, 17 Jul 2019 05:57:31 -0400 From: "Michael S. Tsirkin" To: David Hildenbrand Message-ID: <20190717054727-mutt-send-email-mst@kernel.org> References: <20190717084255.17173-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190717084255.17173-1-david@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Wed, 17 Jul 2019 09:57:39 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH-for-4.1] virtio-balloon: fix QEMU crashes on pagesize > BALLOON_PAGE_SIZE X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Igor Mammedov , David Gibson , qemu-devel@nongnu.org, Stefan Hajnoczi , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Jul 17, 2019 at 10:42:55AM +0200, David Hildenbrand wrote: > We are using the wrong functions to set/clear bits, effectively touching > multiple bits, writing out of range of the bitmap, resulting in memory > corruptions. We have to use set_bit()/clear_bit() instead. > > Can easily be reproduced by starting a qemu guest on hugetlbfs memory, > inflating the balloon. QEMU crashes. This never could have worked > properly - especially, also pages would have been discarded when the > first sub-page would be inflated (the whole bitmap would be set). > > While testing I realized, that on hugetlbfs it is pretty much impossible > to discard a page - the guest just frees the 4k sub-pages in random order > most of the time. I was only able to discard a hugepage a handful of > times - so I hope that now works correctly. > > Fixes: ed48c59875b6 ("virtio-balloon: Safely handle BALLOON_PAGE_SIZE < > host page size") > Fixes: b27b32391404 ("virtio-balloon: Fix possible guest memory corruption > with inflates & deflates") > Cc: qemu-stable@nongnu.org #v4.0.0 > Cc: Stefan Hajnoczi > Cc: David Gibson > Cc: Michael S. Tsirkin > Cc: Igor Mammedov > Signed-off-by: David Hildenbrand > --- > hw/virtio/virtio-balloon.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index e85d1c0d5c..669067d661 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -94,9 +94,8 @@ static void balloon_inflate_page(VirtIOBalloon *balloon, > balloon->pbp->base = host_page_base; > } > > - bitmap_set(balloon->pbp->bitmap, > - (ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, > - subpages); > + set_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, > + balloon->pbp->bitmap); > > if (bitmap_full(balloon->pbp->bitmap, subpages)) { > /* We've accumulated a full host page, we can actually discard > @@ -140,9 +139,8 @@ static void balloon_deflate_page(VirtIOBalloon *balloon, > * for a guest to do this in practice, but handle it anyway, > * since getting it wrong could mean discarding memory the > * guest is still using. */ > - bitmap_clear(balloon->pbp->bitmap, > - (ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, > - subpages); > + clear_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, > + balloon->pbp->bitmap); > > if (bitmap_empty(balloon->pbp->bitmap, subpages)) { > g_free(balloon->pbp); I also started to wonder about this: if (!balloon->pbp) { /* Starting on a new host page */ size_t bitlen = BITS_TO_LONGS(subpages) * sizeof(unsigned long); balloon->pbp = g_malloc0(sizeof(PartiallyBalloonedPage) + bitlen); balloon->pbp->rb = rb; balloon->pbp->base = host_page_base; } Is keeping a pointer to a ram block like this safe? what if the ramblock gets removed? > -- > 2.21.0