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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 9497EC3DA64 for ; Tue, 6 Aug 2024 09:33:31 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sbGZ5-0004xr-GA; Tue, 06 Aug 2024 05:33:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sbGZ3-0004oV-6d for qemu-devel@nongnu.org; Tue, 06 Aug 2024 05:33:09 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sbGZ0-00034G-5c for qemu-devel@nongnu.org; Tue, 06 Aug 2024 05:33:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722936785; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=F30WIPSvFy4+NVmGmvL/VlEj4NDidU1MYee025KwEEA=; b=ARaSmJGfrfuoQIDexWKvGfJN1XW+Y1ycqCsH8NmGLBG+EyvYiogVc6NUGlkhQCbsHxMJZQ 44LTa+IMsR+9JFzlz+q2vGKiIemHFm4xT+CjFIKnCw/ffuteOsuNdOG9JuIoX8V+xe8O+I 8mzK1NyreTqfNSSCGx8yQLOpAjocmBo= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-454-dS08DuSnPTWRSPVOhU4wuw-1; Tue, 06 Aug 2024 05:33:02 -0400 X-MC-Unique: dS08DuSnPTWRSPVOhU4wuw-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 878041955D45; Tue, 6 Aug 2024 09:33:00 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.106]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4C0DA195605A; Tue, 6 Aug 2024 09:32:57 +0000 (UTC) Date: Tue, 6 Aug 2024 10:32:54 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Cc: qemu-devel@nongnu.org, kwolf@redhat.com, hreitz@redhat.com, qemu-block@nongnu.org, den@virtuozzo.com, andrey.drobyshev@virtuozzo.com, alexander.ivanov@virtuozzo.com, vsementsov@yandex-team.ru Subject: Re: [PATCH v3 2/2] nbd: Clean up clients more efficiently Message-ID: References: <20240806022542.381883-4-eblake@redhat.com> <20240806022542.381883-6-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240806022542.381883-6-eblake@redhat.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.143, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Aug 05, 2024 at 09:21:36PM -0500, Eric Blake wrote: > Since an NBD server may be long-living, serving clients that > repeatedly connect and disconnect, it can be more efficient to clean > up after each client disconnects, rather than storing a list of > resources to clean up when the server exits. Rewrite the list of > known clients to be double-linked so that we can get O(1) deletion to > keep the list pruned to size as clients exit. This in turn requires > each client to track an opaque pointer of owner information (although > qemu-nbd doesn't need to refer to it). I tend to feel that this needs to be squashed into the previous patch. The previous patch effectively creates unbounded memory usage in the NBD server. ie consider a client that connects and immediately disconnects, not sending any data, in a tight loop. It will "leak" NBDConn & QIOChanelSocket pointers for each iteration of the loop, only to be cleaned up when the NBD Server is shutdown. Especially given that we tagged the previous commit with a CVE and not this commit, people could be misled into backporting only the former commit leaving them open to the leak. > > Signed-off-by: Eric Blake > --- > include/block/nbd.h | 4 +++- > blockdev-nbd.c | 27 ++++++++++++++++----------- > nbd/server.c | 15 ++++++++++++--- > qemu-nbd.c | 2 +- > 4 files changed, 32 insertions(+), 16 deletions(-) > > diff --git a/include/block/nbd.h b/include/block/nbd.h > index 4e7bd6342f9..7dce9b9c35b 100644 > --- a/include/block/nbd.h > +++ b/include/block/nbd.h > @@ -405,7 +405,9 @@ NBDExport *nbd_export_find(const char *name); > void nbd_client_new(QIOChannelSocket *sioc, > QCryptoTLSCreds *tlscreds, > const char *tlsauthz, > - void (*close_fn)(NBDClient *, bool)); > + void (*close_fn)(NBDClient *, bool), > + void *owner); > +void *nbd_client_owner(NBDClient *client); > void nbd_client_get(NBDClient *client); > void nbd_client_put(NBDClient *client); > > diff --git a/blockdev-nbd.c b/blockdev-nbd.c > index b8f00f402c6..660f89d881e 100644 > --- a/blockdev-nbd.c > +++ b/blockdev-nbd.c > @@ -23,7 +23,7 @@ > > typedef struct NBDConn { > QIOChannelSocket *cioc; > - QSLIST_ENTRY(NBDConn) next; > + QLIST_ENTRY(NBDConn) next; > } NBDConn; > > typedef struct NBDServerData { > @@ -32,10 +32,11 @@ typedef struct NBDServerData { > char *tlsauthz; > uint32_t max_connections; > uint32_t connections; > - QSLIST_HEAD(, NBDConn) conns; > + QLIST_HEAD(, NBDConn) conns; > } NBDServerData; > > static NBDServerData *nbd_server; > +static uint32_t nbd_cookie; /* Generation count of nbd_server */ > static int qemu_nbd_connections = -1; /* Non-negative if this is qemu-nbd */ > > static void nbd_update_server_watch(NBDServerData *s); > @@ -57,10 +58,16 @@ int nbd_server_max_connections(void) > > static void nbd_blockdev_client_closed(NBDClient *client, bool ignored) > { > + NBDConn *conn = nbd_client_owner(client); > + > assert(qemu_in_main_thread() && nbd_server); > > + object_unref(OBJECT(conn->cioc)); > + QLIST_REMOVE(conn, next); > + g_free(conn); > + > nbd_client_put(client); > - assert(nbd_server->connections > 0); > + assert(nbd_server && nbd_server->connections > 0); > nbd_server->connections--; > nbd_update_server_watch(nbd_server); > } > @@ -74,12 +81,12 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc, > nbd_server->connections++; > object_ref(OBJECT(cioc)); > conn->cioc = cioc; > - QSLIST_INSERT_HEAD(&nbd_server->conns, conn, next); > + QLIST_INSERT_HEAD(&nbd_server->conns, conn, next); > nbd_update_server_watch(nbd_server); > > qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server"); > nbd_client_new(cioc, nbd_server->tlscreds, nbd_server->tlsauthz, > - nbd_blockdev_client_closed); > + nbd_blockdev_client_closed, conn); > } > > static void nbd_update_server_watch(NBDServerData *s) > @@ -93,6 +100,8 @@ static void nbd_update_server_watch(NBDServerData *s) > > static void nbd_server_free(NBDServerData *server) > { > + NBDConn *conn, *tmp; > + > if (!server) { > return; > } > @@ -103,14 +112,9 @@ static void nbd_server_free(NBDServerData *server) > */ > qio_net_listener_disconnect(server->listener); > object_unref(OBJECT(server->listener)); > - while (!QSLIST_EMPTY(&server->conns)) { > - NBDConn *conn = QSLIST_FIRST(&server->conns); > - > + QLIST_FOREACH_SAFE(conn, &server->conns, next, tmp) { > qio_channel_shutdown(QIO_CHANNEL(conn->cioc), QIO_CHANNEL_SHUTDOWN_BOTH, > NULL); > - object_unref(OBJECT(conn->cioc)); > - QSLIST_REMOVE_HEAD(&server->conns, next); > - g_free(conn); > } > > AIO_WAIT_WHILE_UNLOCKED(NULL, server->connections > 0); > @@ -119,6 +123,7 @@ static void nbd_server_free(NBDServerData *server) > object_unref(OBJECT(server->tlscreds)); > } > g_free(server->tlsauthz); > + nbd_cookie++; > > g_free(server); > } > diff --git a/nbd/server.c b/nbd/server.c > index 892797bb111..90f48b42a47 100644 > --- a/nbd/server.c > +++ b/nbd/server.c > @@ -124,6 +124,7 @@ struct NBDMetaContexts { > struct NBDClient { > int refcount; /* atomic */ > void (*close_fn)(NBDClient *client, bool negotiated); > + void *owner; > > QemuMutex lock; > > @@ -3205,14 +3206,15 @@ static coroutine_fn void nbd_co_client_start(void *opaque) > } > > /* > - * Create a new client listener using the given channel @sioc. > + * Create a new client listener using the given channel @sioc and @owner. > * Begin servicing it in a coroutine. When the connection closes, call > - * @close_fn with an indication of whether the client completed negotiation. > + * @close_fn and an indication of whether the client completed negotiation. > */ > void nbd_client_new(QIOChannelSocket *sioc, > QCryptoTLSCreds *tlscreds, > const char *tlsauthz, > - void (*close_fn)(NBDClient *, bool)) > + void (*close_fn)(NBDClient *, bool), > + void *owner) > { > NBDClient *client; > Coroutine *co; > @@ -3231,7 +3233,14 @@ void nbd_client_new(QIOChannelSocket *sioc, > client->ioc = QIO_CHANNEL(sioc); > object_ref(OBJECT(client->ioc)); > client->close_fn = close_fn; > + client->owner = owner; > > co = qemu_coroutine_create(nbd_co_client_start, client); > qemu_coroutine_enter(co); > } > + > +void * > +nbd_client_owner(NBDClient *client) > +{ > + return client->owner; > +} > diff --git a/qemu-nbd.c b/qemu-nbd.c > index d7b3ccab21c..da6e36a2a34 100644 > --- a/qemu-nbd.c > +++ b/qemu-nbd.c > @@ -390,7 +390,7 @@ static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc, > > nb_fds++; > nbd_update_server_watch(); > - nbd_client_new(cioc, tlscreds, tlsauthz, nbd_client_closed); > + nbd_client_new(cioc, tlscreds, tlsauthz, nbd_client_closed, NULL); > } > > static void nbd_update_server_watch(void) > -- > 2.45.2 > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|