From patchwork Fri Aug 9 05:48:48 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Wang X-Patchwork-Id: 11085357 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E72D414D5 for ; Fri, 9 Aug 2019 05:49:25 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D3F2528BB8 for ; Fri, 9 Aug 2019 05:49:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C7FE228C28; Fri, 9 Aug 2019 05:49:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=unavailable version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7E87728BB8 for ; Fri, 9 Aug 2019 05:49:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AC0BC6B000E; Fri, 9 Aug 2019 01:49:24 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id A718D6B0010; Fri, 9 Aug 2019 01:49:24 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9874F6B0266; Fri, 9 Aug 2019 01:49:24 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by kanga.kvack.org (Postfix) with ESMTP id 7935F6B000E for ; Fri, 9 Aug 2019 01:49:24 -0400 (EDT) Received: by mail-qk1-f198.google.com with SMTP id c79so84927121qkg.13 for ; Thu, 08 Aug 2019 22:49:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:from:to:cc :subject:date:message-id:in-reply-to:references; bh=B1luxMJLkB4TGmpB4Z6oIauGJZZAFOoy1m4euQKOEm4=; b=PlSWhLHnt2mdBUi0c+gQNi7f4bl/m62dXyay+CX2PTFHqk+ttozhAXT4urxg1NOIxS DAWXLGMMm8Q1+wGNfzfQCY1L2ZBeGkE/SPHasSsssSt2vFAzpCmqusKuf0C1geajWcyX zSloC3LfcRjqUeuF0lv43LiuhCtunCcGS8228lcQpwwHineoHWpSPYrug1gIph09nAXS obvDRoGKUSBYOT4CkEjaag1jBJOb6cH79Drz5RKXhuKsuwEl5i78r67rkkRZWiBmjgqJ SkYqu7xaIqKHSkBMjLw2p5Bi6B1U/pqFskIsLUuD7pajOiMfyEK8h92u9Cb8Ha1oHmxB aIWQ== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of jasowang@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jasowang@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Gm-Message-State: APjAAAWX/oGESYttmXenjmQFswWUhVlci5y2g7p/gMhbz9Te4Roa1HIE 7EOMy0QWvNwnJGOndcqYVBl2mmcZpWhW6Bjhq4SPimi2JS3JDFZvMR+9RRMJx0bTktveYcqZPEO C/w7NUOdwVhmjmjQ9Nas68lXf+1V40Vr0uEeCSgmndy9lNRPJ172tbxSETpCAYPutPw== X-Received: by 2002:a37:274a:: with SMTP id n71mr15486260qkn.448.1565329764312; Thu, 08 Aug 2019 22:49:24 -0700 (PDT) X-Google-Smtp-Source: APXvYqyjPL1NkGVk9oMxe4EpkTOxtDo4SC8VYCgx7AsQ6V8HhdZnx3q9eKrjVCOf9mDWp2Fz2bVj X-Received: by 2002:a37:274a:: with SMTP id n71mr15486240qkn.448.1565329763800; Thu, 08 Aug 2019 22:49:23 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1565329763; cv=none; d=google.com; s=arc-20160816; b=ePfO3ysNU3ucV57xn5QqbNk164yL7Uyt+bnlfMliO4c85IAYB1qMsTZH/lCkDvIVw4 XvptelNvcTQFYggDqReb186M7yKj8Ki/jL91VwYVMitRtJg7fLD2CatC2Oxx5k61sbMD aUzy0M6C9LWNHra/QEPuuwMzamY4GL1vRuqvuT6DJv/eQVrcmmNfzr5UUnz4fyPcZY5H JF2vVk+5RvOJMbvyTV3Hj9jXBnWCCaWfEmZVIB5nKvs1oINqSFQV4f4mx7WsEkbAY6ba jTvWORpTh0TmG5ze0m2ohFnhpzNyQGRbeOPpIuieYBGCgfSSF70naVrVlfVP0tDTL+pS noGg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=references:in-reply-to:message-id:date:subject:cc:to:from; bh=B1luxMJLkB4TGmpB4Z6oIauGJZZAFOoy1m4euQKOEm4=; b=XIZMMP+4i0eI6rDLcY+qsreorwnRuM2x1pbxExqZ3ABDnJ3sQDD+xku8aP+MqpqFaO 0EEGW1E5dLKkKNJkEy6B0uR6Z+3Httc+jRQoOTm+c00zIILpkfKvsi+XM3Rx7rtLd9D1 OWKxzKBYCI6VX+ZDlooDDbyrOfmx/hUGKvJWOFcTIU3b7zZHbo+zNFx+2ZByyDlKHGuj 2JsqYJ/bOZC2dOa0qJ2Ns7tRILI9eZ4YOZNB1tYam2p79Zq7RePhGb0nK5dUGdVl83fv o0ZaWghAqHkrwZ6IqVj+0iWWZYqOs5qVa/5owa4RcE1+mOpzBRglij5FhZ4FnggWvhEZ uQ1Q== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of jasowang@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jasowang@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id a13si1663485qkl.142.2019.08.08.22.49.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Aug 2019 22:49:23 -0700 (PDT) Received-SPF: pass (google.com: domain of jasowang@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jasowang@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jasowang@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com 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 1256B30FB8DE; Fri, 9 Aug 2019 05:49:23 +0000 (UTC) Received: from hp-dl380pg8-01.lab.eng.pek2.redhat.com (hp-dl380pg8-01.lab.eng.pek2.redhat.com [10.73.8.10]) by smtp.corp.redhat.com (Postfix) with ESMTP id C064D5D9D6; Fri, 9 Aug 2019 05:49:16 +0000 (UTC) From: Jason Wang To: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, jgg@ziepe.ca, Jason Wang Subject: [PATCH V5 6/9] vhost: don't do synchronize_rcu() in vhost_uninit_vq_maps() Date: Fri, 9 Aug 2019 01:48:48 -0400 Message-Id: <20190809054851.20118-7-jasowang@redhat.com> In-Reply-To: <20190809054851.20118-1-jasowang@redhat.com> References: <20190809054851.20118-1-jasowang@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 [10.5.110.47]); Fri, 09 Aug 2019 05:49:23 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP There's no need for RCU synchronization in vhost_uninit_vq_maps() since we've already serialized with readers (memory accessors). This also avoid the possible userspace DOS through ioctl() because of the possible high latency caused by synchronize_rcu(). Reported-by: Michael S. Tsirkin Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address") Signed-off-by: Jason Wang --- drivers/vhost/vhost.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c12cdadb0855..cfc11f9ed9c9 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -333,7 +333,9 @@ static void vhost_uninit_vq_maps(struct vhost_virtqueue *vq) } spin_unlock(&vq->mmu_lock); - synchronize_rcu(); + /* No need for synchronize_rcu() or kfree_rcu() since we are + * serialized with memory accessors (e.g vq mutex held). + */ for (i = 0; i < VHOST_NUM_ADDRS; i++) if (map[i])