From nobody Wed Dec 17 05:38:42 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1566489307; cv=none; d=zoho.com; s=zohoarc; b=hrPtdimto2yVW5HdKySGbf24Zu6F+VDScu7b/PYNpnvz0Y5XckVHDSqUiigT81HzbB68QNzG72VkRX5zXSCZWs5Q1J8MQro+6+dJ/EH1Sv//4SXweddhd4ZmPrCx2Rn8efuRTpATZ+PTriCwm9eYZcJL3e4iItOvaf+XzVAF7ig= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1566489307; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To:ARC-Authentication-Results; bh=cyLmZqgsb7Gjes9Rz9l9BcJHu4TUd9Viyc2WQTzz/mc=; b=NDIJVX7VOnBBmL3LvmZMIcF6gIvuBbSLK3vAdnCdztffIMeivYpjq/9ENx2t6RbekT/JU62kYv0JE0CEnYblaFpiicgm5bxFb1j57cDxj3Rg2IsjG/+mJN1mRh5zT5yDZyj01pwTc4vWbA2s3saUEEZXNrONiSHMM76Sb9YDPFk= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1566489307148397.99976344048434; Thu, 22 Aug 2019 08:55:07 -0700 (PDT) Received: from localhost ([::1]:44748 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0pQX-0004RG-0F for importer@patchew.org; Thu, 22 Aug 2019 11:55:05 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57800) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0pOx-0002nU-Nr for qemu-devel@nongnu.org; Thu, 22 Aug 2019 11:53:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i0pOw-0003nJ-Kh for qemu-devel@nongnu.org; Thu, 22 Aug 2019 11:53:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54908) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i0pOu-0003kd-AW; Thu, 22 Aug 2019 11:53:24 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9BB332BFDC; Thu, 22 Aug 2019 15:53:23 +0000 (UTC) Received: from localhost (ovpn-116-61.ams2.redhat.com [10.36.116.61]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3D66E5D772; Thu, 22 Aug 2019 15:53:15 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Date: Thu, 22 Aug 2019 16:53:01 +0100 Message-Id: <20190822155302.20916-2-stefanha@redhat.com> In-Reply-To: <20190822155302.20916-1-stefanha@redhat.com> References: <20190822155302.20916-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 22 Aug 2019 15:53:23 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 1/2] util/async: hold AioContext ref to prevent use-after-free 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: Fam Zheng , Peter Maydell , qemu-block@nongnu.org, "Michael S. Tsirkin" , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" The tests/test-bdrv-drain /bdrv-drain/iothread/drain test case does the following: 1. The preadv coroutine calls aio_bh_schedule_oneshot() and then yields. 2. The one-shot BH executes in another AioContext. All it does is call aio_co_wakeup(preadv_co). 3. The preadv coroutine is re-entered and returns. There is a race condition in aio_co_wake() where the preadv coroutine returns and the test case destroys the preadv IOThread. aio_co_wake() can still be running in the other AioContext and it performs an access to the freed IOThread AioContext. Here is the race in aio_co_schedule(): QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines, co, co_scheduled_next); <-- race: co may execute before we invoke qemu_bh_schedule()! qemu_bh_schedule(ctx->co_schedule_bh); So if co causes ctx to be freed then we're in trouble. Fix this problem by holding a reference to ctx. Signed-off-by: Stefan Hajnoczi Reviewed-by: Paolo Bonzini Message-id: 20190723190623.21537-1-stefanha@redhat.com Message-Id: <20190723190623.21537-1-stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi --- util/async.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/util/async.c b/util/async.c index 8d2105729c..4e4c7af51e 100644 --- a/util/async.c +++ b/util/async.c @@ -459,9 +459,17 @@ void aio_co_schedule(AioContext *ctx, Coroutine *co) abort(); } =20 + /* The coroutine might run and release the last ctx reference before we + * invoke qemu_bh_schedule(). Take a reference to keep ctx alive until + * we're done. + */ + aio_context_ref(ctx); + QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines, co, co_scheduled_next); qemu_bh_schedule(ctx->co_schedule_bh); + + aio_context_unref(ctx); } =20 void aio_co_wake(struct Coroutine *co) --=20 2.21.0