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Subject: [PULL 1/5] nbd: Minor style and typo fixes Date: Thu, 8 Aug 2024 16:53:39 -0500 Message-ID: <20240808215529.1065336-8-eblake@redhat.com> In-Reply-To: <20240808215529.1065336-7-eblake@redhat.com> References: <20240808215529.1065336-7-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.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; Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@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=-0.141, 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_H3=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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1723154240511116600 Touch up a comment with the wrong type name, and an over-long line, both noticed while working on upcoming patches. Signed-off-by: Eric Blake Message-ID: <20240807174943.771624-10-eblake@redhat.com> Reviewed-by: Daniel P. Berrang=C3=A9 --- nbd/server.c | 2 +- qemu-nbd.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/nbd/server.c b/nbd/server.c index 892797bb111..ecd9366ba64 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -1972,7 +1972,7 @@ static void nbd_export_request_shutdown(BlockExport *= blk_exp) blk_exp_ref(&exp->common); /* - * TODO: Should we expand QMP NbdServerRemoveNode enum to allow a + * TODO: Should we expand QMP BlockExportRemoveMode enum to allow a * close mode that stops advertising the export to new clients but * still permits existing clients to run to completion? Because of * that possibility, nbd_export_close() can be called more than diff --git a/qemu-nbd.c b/qemu-nbd.c index d7b3ccab21c..8e104ef22c3 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -588,7 +588,8 @@ int main(int argc, char **argv) pthread_t client_thread; const char *fmt =3D NULL; Error *local_err =3D NULL; - BlockdevDetectZeroesOptions detect_zeroes =3D BLOCKDEV_DETECT_ZEROES_O= PTIONS_OFF; + BlockdevDetectZeroesOptions detect_zeroes =3D + BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF; QDict *options =3D NULL; const char *export_name =3D NULL; /* defaults to "" later for server m= ode */ const char *export_description =3D NULL; --=20 2.46.0 From nobody Sun Nov 24 10:32:09 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1723154209; cv=none; d=zohomail.com; s=zohoarc; b=TK9rRXkOzHl16sX9VB0M1fcu/dHL/MF0BRq798wilN7vEUJT99AWAxRu49hgQx45uDYNtzOq/9WkdM3PQ9dF+Zfq15H65gt/oj++B/0n4VNDPXoron1NyjiWml/T2gRiKwbWaGAf+BCNnUq7HDOtx1ilo6JfuuMoYtUmBTHc3D4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1723154209; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=Ga2Mqu/c8WDWZTYY1BG1jDy0Z9/qdi44vVEuyktmlm8=; b=BGuv9gtsGue1A39Se2ra98rkJE9YhsXF2Z6EjC1e+A4eo0HbX+9ibqm6q+sibxaMvKxR74tbMBOkG71YX/WHfwYOaBqvYXejkE505LBgENFUZSTDexo6xTJaR33AmuX3klYCI5+YQWJZKcO0OYnMPd9hDV9Z4hk/L+4vMg0b6gY= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1723154209073463.87983103285603; Thu, 8 Aug 2024 14:56:49 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1scB6v-000422-VV; Thu, 08 Aug 2024 17:55:54 -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 1scB6r-0003t3-HN for qemu-devel@nongnu.org; Thu, 08 Aug 2024 17:55:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1scB6p-0004au-Jb for qemu-devel@nongnu.org; Thu, 08 Aug 2024 17:55:49 -0400 Received: from mx-prod-mc-03.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-553-Kxt_8kNcPKiPi7wQlZny_A-1; Thu, 08 Aug 2024 17:55:45 -0400 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0FFA619541B4; Thu, 8 Aug 2024 21:55:44 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.114]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 190421956056; Thu, 8 Aug 2024 21:55:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723154146; 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=Ga2Mqu/c8WDWZTYY1BG1jDy0Z9/qdi44vVEuyktmlm8=; b=LII008ln/f56we9pSsYWB4GrOtNd0OsVSPbxBiL7eNpwTO2e2Ob15ZKxYOPds8ZWH7Nd1q z9JN6HAzU9H8uQY+mdSsLqHsw54SAM6ACqUqZG+ryl+teCyMMQRWPpD0ZHFF0JsD7HkfxS XTV/x601H1mrb6AHSlwBt28HRXaMH7c= X-MC-Unique: Kxt_8kNcPKiPi7wQlZny_A-1 From: Eric Blake To: qemu-devel@nongnu.org Cc: Vladimir Sementsov-Ogievskiy , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Kevin Wolf , Hanna Reitz , qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PULL 2/5] nbd/server: Plumb in new args to nbd_client_add() Date: Thu, 8 Aug 2024 16:53:40 -0500 Message-ID: <20240808215529.1065336-9-eblake@redhat.com> In-Reply-To: <20240808215529.1065336-7-eblake@redhat.com> References: <20240808215529.1065336-7-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.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; Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@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=-0.141, 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_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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1723154210610116600 Upcoming patches to fix a CVE need to track an opaque pointer passed in by the owner of a client object, as well as request for a time limit on how fast negotiation must complete. Prepare for that by changing the signature of nbd_client_new() and adding an accessor to get at the opaque pointer, although for now the two servers (qemu-nbd.c and blockdev-nbd.c) do not change behavior even though they pass in a new default timeout value. Suggested-by: Vladimir Sementsov-Ogievskiy Signed-off-by: Eric Blake Message-ID: <20240807174943.771624-11-eblake@redhat.com> Reviewed-by: Daniel P. Berrang=C3=A9 [eblake: s/LIMIT/MAX_SECS/ as suggested by Dan] Signed-off-by: Eric Blake --- include/block/nbd.h | 11 ++++++++++- blockdev-nbd.c | 6 ++++-- nbd/server.c | 20 +++++++++++++++++--- qemu-nbd.c | 4 +++- 4 files changed, 34 insertions(+), 7 deletions(-) diff --git a/include/block/nbd.h b/include/block/nbd.h index 4e7bd6342f9..1d4d65922d1 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -33,6 +33,12 @@ typedef struct NBDMetaContexts NBDMetaContexts; extern const BlockExportDriver blk_exp_nbd; +/* + * NBD_DEFAULT_HANDSHAKE_MAX_SECS: Number of seconds in which client must + * succeed at NBD_OPT_GO before being forcefully dropped as too slow. + */ +#define NBD_DEFAULT_HANDSHAKE_MAX_SECS 10 + /* Handshake phase structs - this struct is passed on the wire */ typedef struct NBDOption { @@ -403,9 +409,12 @@ AioContext *nbd_export_aio_context(NBDExport *exp); NBDExport *nbd_export_find(const char *name); void nbd_client_new(QIOChannelSocket *sioc, + uint32_t handshake_max_secs, 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 213012435f4..267a1de903f 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -64,8 +64,10 @@ static void nbd_accept(QIONetListener *listener, QIOChan= nelSocket *cioc, 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); + /* TODO - expose handshake timeout as QMP option */ + nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS, + nbd_server->tlscreds, nbd_server->tlsauthz, + nbd_blockdev_client_closed, NULL); } static void nbd_update_server_watch(NBDServerData *s) diff --git a/nbd/server.c b/nbd/server.c index ecd9366ba64..fee04415d83 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -124,12 +124,14 @@ struct NBDMetaContexts { struct NBDClient { int refcount; /* atomic */ void (*close_fn)(NBDClient *client, bool negotiated); + void *owner; QemuMutex lock; NBDExport *exp; QCryptoTLSCreds *tlscreds; char *tlsauthz; + uint32_t handshake_max_secs; QIOChannelSocket *sioc; /* The underlying data channel */ QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) = */ @@ -3191,6 +3193,7 @@ static coroutine_fn void nbd_co_client_start(void *op= aque) qemu_co_mutex_init(&client->send_lock); + /* TODO - utilize client->handshake_max_secs */ if (nbd_negotiate(client, &local_err)) { if (local_err) { error_report_err(local_err); @@ -3205,14 +3208,17 @@ 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 negotiatio= n. + * @close_fn with an indication of whether the client completed negotiation + * within @handshake_max_secs seconds (0 for unbounded). */ void nbd_client_new(QIOChannelSocket *sioc, + uint32_t handshake_max_secs, QCryptoTLSCreds *tlscreds, const char *tlsauthz, - void (*close_fn)(NBDClient *, bool)) + void (*close_fn)(NBDClient *, bool), + void *owner) { NBDClient *client; Coroutine *co; @@ -3225,13 +3231,21 @@ void nbd_client_new(QIOChannelSocket *sioc, object_ref(OBJECT(client->tlscreds)); } client->tlsauthz =3D g_strdup(tlsauthz); + client->handshake_max_secs =3D handshake_max_secs; client->sioc =3D sioc; qio_channel_set_delay(QIO_CHANNEL(sioc), false); object_ref(OBJECT(client->sioc)); client->ioc =3D QIO_CHANNEL(sioc); object_ref(OBJECT(client->ioc)); client->close_fn =3D close_fn; + client->owner =3D owner; co =3D 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 8e104ef22c3..a186d2e1190 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -390,7 +390,9 @@ static void nbd_accept(QIONetListener *listener, QIOCha= nnelSocket *cioc, nb_fds++; nbd_update_server_watch(); - nbd_client_new(cioc, tlscreds, tlsauthz, nbd_client_closed); + /* TODO - expose handshake timeout as command line option */ + nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS, + tlscreds, tlsauthz, nbd_client_closed, NULL); } static void nbd_update_server_watch(void) --=20 2.46.0 From nobody Sun Nov 24 10:32:09 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1723154213; cv=none; d=zohomail.com; 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Thu, 8 Aug 2024 21:55:46 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.114]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3F62519560A3; Thu, 8 Aug 2024 21:55:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723154153; 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=Zp1LX7WiE/Tm338u5H0qM12wvmECy6jktr7yJcf8lSE=; b=CxkEGkl0I8g8fHU11u1rLzbaVj1rsBEdL1D2JRmAAFMdPROBmF8BSYdxPLxbNYHP1hBVPD wRe30O5otAV4BU8X1HCJHSu3QFuurHMfveMhd7ebuq1qNKiUkIGArVSfS9EWhu9DWj/muE sYe/lktuNdq3niFLHdIuITA0ymBdKiQ= X-MC-Unique: LupBeObbO7aZih9im9sAkA-1 From: Eric Blake To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Kevin Wolf , Hanna Reitz , Vladimir Sementsov-Ogievskiy , Markus Armbruster , qemu-block@nongnu.org (open list:Block layer core) Subject: [PULL 3/5] nbd/server: CVE-2024-7409: Cap default max-connections to 100 Date: Thu, 8 Aug 2024 16:53:41 -0500 Message-ID: <20240808215529.1065336-10-eblake@redhat.com> In-Reply-To: <20240808215529.1065336-7-eblake@redhat.com> References: <20240808215529.1065336-7-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.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; Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@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=-0.141, 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=ham 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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1723154214709116600 Allowing an unlimited number of clients to any web service is a recipe for a rudimentary denial of service attack: the client merely needs to open lots of sockets without closing them, until qemu no longer has any more fds available to allocate. For qemu-nbd, we default to allowing only 1 connection unless more are explicitly asked for (-e or --shared); this was historically picked as a nice default (without an explicit -t, a non-persistent qemu-nbd goes away after a client disconnects, without needing any additional follow-up commands), and we are not going to change that interface now (besides, someday we want to point people towards qemu-storage-daemon instead of qemu-nbd). But for qemu proper, and the newer qemu-storage-daemon, the QMP nbd-server-start command has historically had a default of unlimited number of connections, in part because unlike qemu-nbd it is inherently persistent until nbd-server-stop. Allowing multiple client sockets is particularly useful for clients that can take advantage of MULTI_CONN (creating parallel sockets to increase throughput), although known clients that do so (such as libnbd's nbdcopy) typically use only 8 or 16 connections (the benefits of scaling diminish once more sockets are competing for kernel attention). Picking a number large enough for typical use cases, but not unlimited, makes it slightly harder for a malicious client to perform a denial of service merely by opening lots of connections withot progressing through the handshake. This change does not eliminate CVE-2024-7409 on its own, but reduces the chance for fd exhaustion or unlimited memory usage as an attack surface. On the other hand, by itself, it makes it more obvious that with a finite limit, we have the problem of an unauthenticated client holding 100 fds opened as a way to block out a legitimate client from being able to connect; thus, later patches will further add timeouts to reject clients that are not making progress. This is an INTENTIONAL change in behavior, and will break any client of nbd-server-start that was not passing an explicit max-connections parameter, yet expects more than 100 simultaneous connections. We are not aware of any such client (as stated above, most clients aware of MULTI_CONN get by just fine on 8 or 16 connections, and probably cope with later connections failing by relying on the earlier connections; libvirt has not yet been passing max-connections, but generally creates NBD servers with the intent for a single client for the sake of live storage migration; meanwhile, the KubeSAN project anticipates a large cluster sharing multiple clients [up to 8 per node, and up to 100 nodes in a cluster], but it currently uses qemu-nbd with an explicit --shared=3D0 rather than qemu-storage-daemon with nbd-server-start). We considered using a deprecation period (declare that omitting max-parameters is deprecated, and make it mandatory in 3 releases - then we don't need to pick an arbitrary default); that has zero risk of breaking any apps that accidentally depended on more than 100 connections, and where such breakage might not be noticed under unit testing but only under the larger loads of production usage. But it does not close the denial-of-service hole until far into the future, and requires all apps to change to add the parameter even if 100 was good enough. It also has a drawback that any app (like libvirt) that is accidentally relying on an unlimited default should seriously consider their own CVE now, at which point they are going to change to pass explicit max-connections sooner than waiting for 3 qemu releases. Finally, if our changed default breaks an app, that app can always pass in an explicit max-parameters with a larger value. It is also intentional that the HMP interface to nbd-server-start is not changed to expose max-connections (any client needing to fine-tune things should be using QMP). Suggested-by: Daniel P. Berrang=C3=A9 Signed-off-by: Eric Blake Message-ID: <20240807174943.771624-12-eblake@redhat.com> Reviewed-by: Daniel P. Berrang=C3=A9 [ericb: Expand commit message to summarize Dan's argument for why we break corner-case back-compat behavior without a deprecation period] Signed-off-by: Eric Blake --- qapi/block-export.json | 4 ++-- include/block/nbd.h | 7 +++++++ block/monitor/block-hmp-cmds.c | 3 ++- blockdev-nbd.c | 8 ++++++++ 4 files changed, 19 insertions(+), 3 deletions(-) diff --git a/qapi/block-export.json b/qapi/block-export.json index 665d5fd0262..ce33fe378df 100644 --- a/qapi/block-export.json +++ b/qapi/block-export.json @@ -28,7 +28,7 @@ # @max-connections: The maximum number of connections to allow at the # same time, 0 for unlimited. Setting this to 1 also stops the # server from advertising multiple client support (since 5.2; -# default: 0) +# default: 100) # # Since: 4.2 ## @@ -63,7 +63,7 @@ # @max-connections: The maximum number of connections to allow at the # same time, 0 for unlimited. Setting this to 1 also stops the # server from advertising multiple client support (since 5.2; -# default: 0). +# default: 100). # # Errors: # - if the server is already running diff --git a/include/block/nbd.h b/include/block/nbd.h index 1d4d65922d1..d4f8b21aecc 100644 --- a/include/block/nbd.h +++ b/include/block/nbd.h @@ -39,6 +39,13 @@ extern const BlockExportDriver blk_exp_nbd; */ #define NBD_DEFAULT_HANDSHAKE_MAX_SECS 10 +/* + * NBD_DEFAULT_MAX_CONNECTIONS: Number of client sockets to allow at + * once; must be large enough to allow a MULTI_CONN-aware client like + * nbdcopy to create its typical number of 8-16 sockets. + */ +#define NBD_DEFAULT_MAX_CONNECTIONS 100 + /* Handshake phase structs - this struct is passed on the wire */ typedef struct NBDOption { diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c index d954bec6f1e..bdf2eb50b68 100644 --- a/block/monitor/block-hmp-cmds.c +++ b/block/monitor/block-hmp-cmds.c @@ -402,7 +402,8 @@ void hmp_nbd_server_start(Monitor *mon, const QDict *qd= ict) goto exit; } - nbd_server_start(addr, NULL, NULL, 0, &local_err); + nbd_server_start(addr, NULL, NULL, NBD_DEFAULT_MAX_CONNECTIONS, + &local_err); qapi_free_SocketAddress(addr); if (local_err !=3D NULL) { goto exit; diff --git a/blockdev-nbd.c b/blockdev-nbd.c index 267a1de903f..24ba5382db0 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -170,6 +170,10 @@ void nbd_server_start(SocketAddress *addr, const char = *tls_creds, void nbd_server_start_options(NbdServerOptions *arg, Error **errp) { + if (!arg->has_max_connections) { + arg->max_connections =3D NBD_DEFAULT_MAX_CONNECTIONS; + } + nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz, arg->max_connections, errp); } @@ -182,6 +186,10 @@ void qmp_nbd_server_start(SocketAddressLegacy *addr, { SocketAddress *addr_flat =3D socket_address_flatten(addr); + if (!has_max_connections) { + max_connections =3D NBD_DEFAULT_MAX_CONNECTIONS; + } + nbd_server_start(addr_flat, tls_creds, tls_authz, max_connections, err= p); qapi_free_SocketAddress(addr_flat); 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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723154150; 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=ZsKmWGYl1FCCzGUB0I+eE+oG1CKKLVObfir/0TYGWI0=; b=jFpwHmwNzpK5P0VJsJPToW5LEzdWxN85kCL/OelSBtx/idVoMTxSNpYB89O5liTet76tJv WTHvwlO/88XTbSv21f+4mabQbaVyIN31dcUfLEfW8GA2EHu9IT2kHqrbW4lBOVDdxhULOr CX5mip0Wb2AXmfVVbpqisCHOc/wXDWA= X-MC-Unique: ktFTkvJYOIyun1Wy22Bw7Q-1 From: Eric Blake To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PULL 4/5] nbd/server: CVE-2024-7409: Drop non-negotiating clients Date: Thu, 8 Aug 2024 16:53:42 -0500 Message-ID: <20240808215529.1065336-11-eblake@redhat.com> In-Reply-To: <20240808215529.1065336-7-eblake@redhat.com> References: <20240808215529.1065336-7-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.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; Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@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=-0.141, 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: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1723154232900116600 A client that opens a socket but does not negotiate is merely hogging qemu's resources (an open fd and a small amount of memory); and a malicious client that can access the port where NBD is listening can attempt a denial of service attack by intentionally opening and abandoning lots of unfinished connections. The previous patch put a default bound on the number of such ongoing connections, but once that limit is hit, no more clients can connect (including legitimate ones). The solution is to insist that clients complete handshake within a reasonable time limit, defaulting to 10 seconds. A client that has not successfully completed NBD_OPT_GO by then (including the case of where the client didn't know TLS credentials to even reach the point of NBD_OPT_GO) is wasting our time and does not deserve to stay connected. Later patches will allow fine-tuning the limit away from the default value (including disabling it for doing integration testing of the handshake process itself). Note that this patch in isolation actually makes it more likely to see qemu SEGV after nbd-server-stop, as any client socket still connected when the server shuts down will now be closed after 10 seconds rather than at the client's whims. That will be addressed in the next patch. For a demo of this patch in action: $ qemu-nbd -f raw -r -t -e 10 file & $ nbdsh --opt-mode -c ' H =3D list() for i in range(20): print(i) H.insert(i, nbd.NBD()) H[i].set_opt_mode(True) H[i].connect_uri("nbd://localhost") ' $ kill $! where later connections get to start progressing once earlier ones are forcefully dropped for taking too long, rather than hanging. Suggested-by: Daniel P. Berrang=C3=A9 Signed-off-by: Eric Blake Message-ID: <20240807174943.771624-13-eblake@redhat.com> Reviewed-by: Daniel P. Berrang=C3=A9 [eblake: rebase to changes earlier in series, reduce scope of timer] Signed-off-by: Eric Blake --- nbd/server.c | 28 +++++++++++++++++++++++++++- nbd/trace-events | 1 + 2 files changed, 28 insertions(+), 1 deletion(-) diff --git a/nbd/server.c b/nbd/server.c index fee04415d83..c30e687fc8b 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -3186,22 +3186,48 @@ static void nbd_client_receive_next_request(NBDClie= nt *client) } } +static void nbd_handshake_timer_cb(void *opaque) +{ + QIOChannel *ioc =3D opaque; + + trace_nbd_handshake_timer_cb(); + qio_channel_shutdown(ioc, QIO_CHANNEL_SHUTDOWN_BOTH, NULL); +} + static coroutine_fn void nbd_co_client_start(void *opaque) { NBDClient *client =3D opaque; Error *local_err =3D NULL; + QEMUTimer *handshake_timer =3D NULL; qemu_co_mutex_init(&client->send_lock); - /* TODO - utilize client->handshake_max_secs */ + /* + * Create a timer to bound the time spent in negotiation. If the + * timer expires, it is likely nbd_negotiate will fail because the + * socket was shutdown. + */ + if (client->handshake_max_secs > 0) { + handshake_timer =3D aio_timer_new(qemu_get_aio_context(), + QEMU_CLOCK_REALTIME, + SCALE_NS, + nbd_handshake_timer_cb, + client->sioc); + timer_mod(handshake_timer, + qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + + client->handshake_max_secs * NANOSECONDS_PER_SECOND); + } + if (nbd_negotiate(client, &local_err)) { if (local_err) { error_report_err(local_err); } + timer_free(handshake_timer); client_close(client, false); return; } + timer_free(handshake_timer); WITH_QEMU_LOCK_GUARD(&client->lock) { nbd_client_receive_next_request(client); } diff --git a/nbd/trace-events b/nbd/trace-events index 00ae3216a11..cbd0a4ab7e4 100644 --- a/nbd/trace-events +++ b/nbd/trace-events @@ -76,6 +76,7 @@ nbd_co_receive_request_payload_received(uint64_t cookie, = uint64_t len) "Payload nbd_co_receive_ext_payload_compliance(uint64_t from, uint64_t len) "client= sent non-compliant write without payload flag: from=3D0x%" PRIx64 ", len= =3D0x%" PRIx64 nbd_co_receive_align_compliance(const char *op, uint64_t from, uint64_t le= n, uint32_t align) "client sent non-compliant unaligned %s request: from=3D= 0x%" PRIx64 ", len=3D0x%" PRIx64 ", align=3D0x%" PRIx32 nbd_trip(void) "Reading request" +nbd_handshake_timer_cb(void) "client took too long to negotiate" # client-connection.c nbd_connect_thread_sleep(uint64_t timeout) "timeout %" PRIu64 --=20 2.46.0 From nobody Sun Nov 24 10:32:09 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; 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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723154157; 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=+5iU9LB2E3O0PDnhsjwEqtsg67UbfnMEfpszk0PbmhQ=; b=VORAdIk7vRs06dPT9MuTubP4MoFDJhsrKjXFHSRL5wir26d7WYCSBeNA7vmmzsV29VtNM+ sXBmSwb/oD8CryLeywBqW6QK9rO884f/le23mdkAflJuXKyz6zvJlTmQCpTLDc6QFR9EMK UcgvfHAA/rd7FYevqMEPX4O/zUvnSnY= X-MC-Unique: 3uE9KF5tPJGEZZe7okkkCw-1 From: Eric Blake To: qemu-devel@nongnu.org Cc: Alexander Ivanov , qemu-stable@nongnu.org, =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Vladimir Sementsov-Ogievskiy , Kevin Wolf , Hanna Reitz , qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PULL 5/5] nbd/server: CVE-2024-7409: Close stray clients at server-stop Date: Thu, 8 Aug 2024 16:53:43 -0500 Message-ID: <20240808215529.1065336-12-eblake@redhat.com> In-Reply-To: <20240808215529.1065336-7-eblake@redhat.com> References: <20240808215529.1065336-7-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.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; Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@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=-0.141, 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_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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1723154214684116600 A malicious client can attempt to connect to an NBD server, and then intentionally delay progress in the handshake, including if it does not know the TLS secrets. Although the previous two patches reduce this behavior by capping the default max-connections parameter and killing slow clients, they did not eliminate the possibility of a client waiting to close the socket until after the QMP nbd-server-stop command is executed, at which point qemu would SEGV when trying to dereference the NULL nbd_server global which is no longer present. This amounts to a denial of service attack. Worse, if another NBD server is started before the malicious client disconnects, I cannot rule out additional adverse effects when the old client interferes with the connection count of the new server (although the most likely is a crash due to an assertion failure when checking nbd_server->connections > 0). For environments without this patch, the CVE can be mitigated by ensuring (such as via a firewall) that only trusted clients can connect to an NBD server. Note that using frameworks like libvirt that ensure that TLS is used and that nbd-server-stop is not executed while any trusted clients are still connected will only help if there is also no possibility for an untrusted client to open a connection but then stall on the NBD handshake. Given the previous patches, it would be possible to guarantee that no clients remain connected by having nbd-server-stop sleep for longer than the default handshake deadline before finally freeing the global nbd_server object, but that could make QMP non-responsive for a long time. So intead, this patch fixes the problem by tracking all client sockets opened while the server is running, and forcefully closing any such sockets remaining without a completed handshake at the time of nbd-server-stop, then waiting until the coroutines servicing those sockets notice the state change. nbd-server-stop now has a second AIO_WAIT_WHILE_UNLOCKED (the first is indirectly through the blk_exp_close_all_type() that disconnects all clients that completed handshakes), but forced socket shutdown is enough to progress the coroutines and quickly tear down all clients before the server is freed, thus finally fixing the CVE. This patch relies heavily on the fact that nbd/server.c guarantees that it only calls nbd_blockdev_client_closed() from the main loop (see the assertion in nbd_client_put() and the hoops used in nbd_client_put_nonzero() to achieve that); if we did not have that guarantee, we would also need a mutex protecting our accesses of the list of connections to survive re-entrancy from independent iothreads. Although I did not actually try to test old builds, it looks like this problem has existed since at least commit 862172f45c (v2.12.0, 2017) - even back when that patch started using a QIONetListener to handle listening on multiple sockets, nbd_server_free() was already unaware that the nbd_blockdev_client_closed callback can be reached later by a client thread that has not completed handshakes (and therefore the client's socket never got added to the list closed in nbd_export_close_all), despite that patch intentionally tearing down the QIONetListener to prevent new clients. Reported-by: Alexander Ivanov Fixes: CVE-2024-7409 CC: qemu-stable@nongnu.org Signed-off-by: Eric Blake Message-ID: <20240807174943.771624-14-eblake@redhat.com> Reviewed-by: Daniel P. Berrang=C3=A9 --- blockdev-nbd.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/blockdev-nbd.c b/blockdev-nbd.c index 24ba5382db0..f73409ae494 100644 --- a/blockdev-nbd.c +++ b/blockdev-nbd.c @@ -21,12 +21,18 @@ #include "io/channel-socket.h" #include "io/net-listener.h" +typedef struct NBDConn { + QIOChannelSocket *cioc; + QLIST_ENTRY(NBDConn) next; +} NBDConn; + typedef struct NBDServerData { QIONetListener *listener; QCryptoTLSCreds *tlscreds; char *tlsauthz; uint32_t max_connections; uint32_t connections; + QLIST_HEAD(, NBDConn) conns; } NBDServerData; static NBDServerData *nbd_server; @@ -51,6 +57,14 @@ int nbd_server_max_connections(void) static void nbd_blockdev_client_closed(NBDClient *client, bool ignored) { + NBDConn *conn =3D 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); nbd_server->connections--; @@ -60,14 +74,20 @@ static void nbd_blockdev_client_closed(NBDClient *clien= t, bool ignored) static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc, gpointer opaque) { + NBDConn *conn =3D g_new0(NBDConn, 1); + + assert(qemu_in_main_thread() && nbd_server); nbd_server->connections++; + object_ref(OBJECT(cioc)); + conn->cioc =3D cioc; + QLIST_INSERT_HEAD(&nbd_server->conns, conn, next); nbd_update_server_watch(nbd_server); qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server"); /* TODO - expose handshake timeout as QMP option */ nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS, nbd_server->tlscreds, nbd_server->tlsauthz, - nbd_blockdev_client_closed, NULL); + nbd_blockdev_client_closed, conn); } static void nbd_update_server_watch(NBDServerData *s) @@ -81,12 +101,25 @@ static void nbd_update_server_watch(NBDServerData *s) static void nbd_server_free(NBDServerData *server) { + NBDConn *conn, *tmp; + if (!server) { return; } + /* + * Forcefully close the listener socket, and any clients that have + * not yet disconnected on their own. + */ qio_net_listener_disconnect(server->listener); object_unref(OBJECT(server->listener)); + QLIST_FOREACH_SAFE(conn, &server->conns, next, tmp) { + qio_channel_shutdown(QIO_CHANNEL(conn->cioc), QIO_CHANNEL_SHUTDOWN= _BOTH, + NULL); + } + + AIO_WAIT_WHILE_UNLOCKED(NULL, server->connections > 0); + if (server->tlscreds) { object_unref(OBJECT(server->tlscreds)); } --=20 2.46.0