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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 12099C5CFE7 for ; Wed, 11 Jul 2018 19:30:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C3D072087C for ; Wed, 11 Jul 2018 19:30:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C3D072087C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388052AbeGKTgR (ORCPT ); Wed, 11 Jul 2018 15:36:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:27535 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387634AbeGKTgR (ORCPT ); Wed, 11 Jul 2018 15:36:17 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A89C430832ED; Wed, 11 Jul 2018 19:30:30 +0000 (UTC) Received: from t450s.home (ovpn-116-29.phx2.redhat.com [10.3.116.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0AD3E16BFC; Wed, 11 Jul 2018 19:30:27 +0000 (UTC) Date: Wed, 11 Jul 2018 13:30:26 -0600 From: Alex Williamson To: Alexey Khoroshilov Cc: Gerd Hoffmann , Kirti Wankhede , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org Subject: Re: [PATCH] sample: vfio-mdev: avoid deadlock in mdev_access() Message-ID: <20180711133026.5339589d@t450s.home> In-Reply-To: <1530910206-24948-1-git-send-email-khoroshilov@ispras.ru> References: <1530910206-24948-1-git-send-email-khoroshilov@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Wed, 11 Jul 2018 19:30:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Jul 2018 23:50:06 +0300 Alexey Khoroshilov wrote: > mdev_access() calls mbochs_get_page() with mdev_state->ops_lock held, > while mbochs_get_page() locks the mutex by itself. > It leads to unavoidable deadlock. > > Found by Linux Driver Verification project (linuxtesting.org). > > Signed-off-by: Alexey Khoroshilov > --- > samples/vfio-mdev/mbochs.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c > index 2960e26c6ea4..6295a21381eb 100644 > --- a/samples/vfio-mdev/mbochs.c > +++ b/samples/vfio-mdev/mbochs.c > @@ -178,6 +178,8 @@ static const char *vbe_name(u32 index) > return "(invalid)"; > } > > +static struct page *__mbochs_get_page(struct mdev_state *mdev_state, > + pgoff_t pgoff); > static struct page *mbochs_get_page(struct mdev_state *mdev_state, > pgoff_t pgoff); > > @@ -394,7 +396,7 @@ static ssize_t mdev_access(struct mdev_device *mdev, char *buf, size_t count, > MBOCHS_MEMORY_BAR_OFFSET + mdev_state->memsize) { > pos -= MBOCHS_MMIO_BAR_OFFSET; > poff = pos & ~PAGE_MASK; > - pg = mbochs_get_page(mdev_state, pos >> PAGE_SHIFT); > + pg = __mbochs_get_page(mdev_state, pos >> PAGE_SHIFT); > map = kmap(pg); > if (is_write) > memcpy(map + poff, buf, count); Looks good, applied to vfio for-linus branch for v4.18. Thanks, Alex