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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 26D91C433E6 for ; Wed, 10 Mar 2021 11:52:48 +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 5420964F76 for ; Wed, 10 Mar 2021 11:52:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5420964F76 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]:39410 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lJxOQ-0006lm-6H for qemu-devel@archiver.kernel.org; Wed, 10 Mar 2021 06:52:46 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55604) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lJxNr-0006MJ-33 for qemu-devel@nongnu.org; Wed, 10 Mar 2021 06:52:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:20175) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lJxNo-00088r-LH for qemu-devel@nongnu.org; Wed, 10 Mar 2021 06:52:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615377127; h=from:from:reply-to:subject:subject: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=xtbInmUCp4Z0fIv/L/UUsURE18vQEZMyVouvG8i8kUs=; b=NojeLkkpVthHqcyYgq5J6bHpE7v6DRAg04Go9h7wnRuhUZsFpedmDFZ8hn+3ggQTyfLGzy NpEAwUKMWwmMfayRgZb7h52GGYRLhjHNcaqbFYUUXfUwdB314OBCqEodPr+mrcD35FLjSg iB4jNvXNo2+w7wyoh6YnxxuwkNl+OFo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-431-6h9NBDc5O0mJfBAz8ZxwJA-1; Wed, 10 Mar 2021 06:52:03 -0500 X-MC-Unique: 6h9NBDc5O0mJfBAz8ZxwJA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BD72526862; Wed, 10 Mar 2021 11:52:02 +0000 (UTC) Received: from merkur.fritz.box (ovpn-114-29.ams2.redhat.com [10.36.114.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E741F1037EBA; Wed, 10 Mar 2021 11:51:58 +0000 (UTC) Date: Wed, 10 Mar 2021 12:51:57 +0100 From: Kevin Wolf To: Max Reitz Subject: Re: [PATCH 0/2] block/curl: Disconnect sockets from CURLState Message-ID: <20210310115157.GB6076@merkur.fritz.box> References: <20210309130541.37540-1-mreitz@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210309130541.37540-1-mreitz@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 09.03.2021 um 14:05 hat Max Reitz geschrieben: > Hi, > > There’s been a bug report concerning our curl driver on Launchpad: > https://bugs.launchpad.net/qemu/+bug/1916501 > > When downloading an image from a certain URL, it crashes. > (https://download.cirros-cloud.net/0.4.0/cirros-0.4.0-x86_64-disk.img) > > The crash is a use-after-free: A CURLState (which basically represents a > transfer) has several CURLSocket objects (encapsulating an FD) over > which the data is transmitted. Once that transfer is done, the state is > purged and all CURLSocket objects belonging to it are freed, under the > assumption that once the transfer is done, the sockets are no longer > used. > > That seems to work with most servers. > > However, I suspect that in the above case, some sockets might be reused > for later transfers; so libcurl doesn’t actually tell us to drop them > (by invoking curl_sock_cb() with CURL_POLL_REMOVE), and that means our > AIO handler (curl_multi_do()) is invoked for some socket after its > corresponding CURLSocket object is freed, leading to said > use-after-free. > > I don’t think libcurl actually says anywhere that sockets are bound to > CURL states (“CURL” objects), though one is always passed to > curl_sock_cb(). But I can’t find any mention that a socket might not be > reused by some other state. > > In fact, there is absolutely no necessity to bind sockets to states. We > can trivially replace the CURLState pointer in CURLSocket by a > BDRVCURLState pointer (patch 1), and very easily move the sockets from a > per-state list to a global hash table (patch 2). > > By doing so, there is no longer any need to free any socket object when > purging a CURLState, because the sockets are then independent of any > such state. (As far as I can tell from testing, this does not lead to > any memory leaks. For every socket there is, libcurl does tell us > eventually to remove it by invoking curl_sock_cb() with > CURL_POLL_REMOVE.) Thanks, applied to the block branch. Kevin