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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 703ACC2D0E4 for ; Mon, 23 Nov 2020 13:28:35 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 176B82080A for ; Mon, 23 Nov 2020 13:28:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="EgFofeHv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 176B82080A Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.34282.65209 (Exim 4.92) (envelope-from ) id 1khBtH-0007cC-KM; Mon, 23 Nov 2020 13:28:23 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 34282.65209; Mon, 23 Nov 2020 13:28:23 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1khBtH-0007c4-HN; Mon, 23 Nov 2020 13:28:23 +0000 Received: by outflank-mailman (input) for mailman id 34282; Mon, 23 Nov 2020 13:28:23 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1khBtH-0007bu-10 for xen-devel@lists.xenproject.org; Mon, 23 Nov 2020 13:28:23 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 4042d843-f1e3-460f-8058-9a1bce6b1987; Mon, 23 Nov 2020 13:28:22 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9301EAC2E; Mon, 23 Nov 2020 13:28:21 +0000 (UTC) Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1khBtH-0007bu-10 for xen-devel@lists.xenproject.org; Mon, 23 Nov 2020 13:28:23 +0000 X-Inumbo-ID: 4042d843-f1e3-460f-8058-9a1bce6b1987 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 4042d843-f1e3-460f-8058-9a1bce6b1987; Mon, 23 Nov 2020 13:28:22 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1606138101; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iIpBVVXINJLxyaNZ9rqCJ2+moiWnSKhQgi3f+gHmkr8=; b=EgFofeHvZq1Fx66zNAN6E4Q4VugkMnnfcWFLj8KxcOTmhCeOukza8WnCGFLzVnKTFcm/ir zAEEJF6COD36UNpZwf58ys3aWyZ9/KswF/a4pii1PwWvM20Qm0dvqAHlcuRxBNbCEvUHdT +3Akux17DQg3KI22vTYdsBRKKcrarW0= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9301EAC2E; Mon, 23 Nov 2020 13:28:21 +0000 (UTC) Subject: [PATCH v3 2/5] evtchn: avoid access tearing for ->virq_to_evtchn[] accesses From: Jan Beulich To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Wei Liu , Stefano Stabellini References: <9d7a052a-6222-80ff-cbf1-612d4ca50c2a@suse.com> Message-ID: Date: Mon, 23 Nov 2020 14:28:21 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <9d7a052a-6222-80ff-cbf1-612d4ca50c2a@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Use {read,write}_atomic() to exclude any eventualities, in particular observing that accesses aren't all happening under a consistent lock. Requested-by: Julien Grall Signed-off-by: Jan Beulich --- v3: New. --- a/xen/common/event_channel.c +++ b/xen/common/event_channel.c @@ -446,7 +446,7 @@ int evtchn_bind_virq(evtchn_bind_virq_t spin_lock(&d->event_lock); - if ( v->virq_to_evtchn[virq] != 0 ) + if ( read_atomic(&v->virq_to_evtchn[virq]) ) ERROR_EXIT(-EEXIST); if ( port != 0 ) @@ -474,7 +474,8 @@ int evtchn_bind_virq(evtchn_bind_virq_t evtchn_write_unlock(chn); - v->virq_to_evtchn[virq] = bind->port = port; + bind->port = port; + write_atomic(&v->virq_to_evtchn[virq], port); out: spin_unlock(&d->event_lock); @@ -660,9 +661,9 @@ int evtchn_close(struct domain *d1, int case ECS_VIRQ: for_each_vcpu ( d1, v ) { - if ( v->virq_to_evtchn[chn1->u.virq] != port1 ) + if ( read_atomic(&v->virq_to_evtchn[chn1->u.virq]) != port1 ) continue; - v->virq_to_evtchn[chn1->u.virq] = 0; + write_atomic(&v->virq_to_evtchn[chn1->u.virq], 0); spin_barrier(&v->virq_lock); } break; @@ -801,7 +802,7 @@ bool evtchn_virq_enabled(const struct vc if ( virq_is_global(virq) && v->vcpu_id ) v = domain_vcpu(v->domain, 0); - return v->virq_to_evtchn[virq]; + return read_atomic(&v->virq_to_evtchn[virq]); } void send_guest_vcpu_virq(struct vcpu *v, uint32_t virq) @@ -814,7 +815,7 @@ void send_guest_vcpu_virq(struct vcpu *v spin_lock_irqsave(&v->virq_lock, flags); - port = v->virq_to_evtchn[virq]; + port = read_atomic(&v->virq_to_evtchn[virq]); if ( unlikely(port == 0) ) goto out; @@ -843,7 +844,7 @@ void send_guest_global_virq(struct domai spin_lock_irqsave(&v->virq_lock, flags); - port = v->virq_to_evtchn[virq]; + port = read_atomic(&v->virq_to_evtchn[virq]); if ( unlikely(port == 0) ) goto out;