From nobody Mon Feb 9 16:18:56 2026 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=1684180535; cv=none; d=zohomail.com; s=zohoarc; b=kNBKEfRrfjGsSIgBNahMXJONTRPbBZFU8lFW5HhVgkvRe+ivJTxGD5OjBwnjsS9q4q+MWIDDbECF0ez5thwkoZ5X9/JyznJOEsG1+DXUVBQLUWTt3DLTtrJg03bSqx5VBcnTr4HEVYrkdKFvuiw+DwqmyicBp1WVvu9Gw3zWx4g= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1684180535; h=Content-Type: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; bh=kekzPRHFKJgpDSEAFBMlc6bgjJDBcKoCLJYFTbydaxA=; b=KP2E98vTwSnnykWzYtg7I0lEiwmYTcrzKCAhKrFdWrQUySJo1+cdKmJMmuN5300+t0beB8/gZ1NnTbgd+HkjDGIy0MIW+E1yken0qEdFCQp148UjaLZJBmhMvJr28PWqBtdN7TNJ781hj2iyDw97bV6h54Pq+/xbAWI2isdM+1w= 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 1684180535462145.6436934465445; Mon, 15 May 2023 12:55:35 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pyeGZ-0004xB-3z; Mon, 15 May 2023 15:53:55 -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 1pyeGX-0004wD-F0 for qemu-devel@nongnu.org; Mon, 15 May 2023 15:53:53 -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 1pyeGW-000482-1O for qemu-devel@nongnu.org; Mon, 15 May 2023 15:53:53 -0400 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-85-_NrVXl8PNR-7mAyeHgFoqw-1; Mon, 15 May 2023 15:53:47 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7726B800047; Mon, 15 May 2023 19:53:47 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 08F43140E917; Mon, 15 May 2023 19:53:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684180431; 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=kekzPRHFKJgpDSEAFBMlc6bgjJDBcKoCLJYFTbydaxA=; b=RvhKmLxlYrvHekzwC0GEPEFpiJ6aA4jeF4wdjhbYbFch7pvGB/psoen0HR+zWM1hYG3V45 FfbHPyginmOytnqMov0nQAbMRTDWneOTWH0YFWa4PWfms/LDouw8GntXjHM0LLWoba3Osu TVS1+RNbgYcdz/ve2i5AvdFLGzt38go= X-MC-Unique: _NrVXl8PNR-7mAyeHgFoqw-1 From: Eric Blake To: qemu-devel@nongnu.org Cc: libguestfs@redhat.com, vsementsov@yandex-team.ru, qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PATCH v3 02/14] nbd/client: Add safety check on chunk payload length Date: Mon, 15 May 2023 14:53:31 -0500 Message-Id: <20230515195343.1915857-3-eblake@redhat.com> In-Reply-To: <20230515195343.1915857-1-eblake@redhat.com> References: <20230515195343.1915857-1-eblake@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: 1684180536273100001 Content-Type: text/plain; charset="utf-8" Our existing use of structured replies either reads into a qiov capped at 32M (NBD_CMD_READ) or caps allocation to 1000 bytes (see NBD_MAX_MALLOC_PAYLOAD in block/nbd.c). But the existing length checks are rather late; if we encounter a buggy (or malicious) server that sends a super-large payload length, we should drop the connection right then rather than assuming the layer on top will be careful. This becomes more important when we permit 64-bit lengths which are even more likely to have the potential for attempted denial of service abuse. Signed-off-by: Eric Blake Reviewed-by: Vladimir Sementsov-Ogievskiy --- nbd/client.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/nbd/client.c b/nbd/client.c index ff75722e487..46f476400ab 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -1413,6 +1413,18 @@ static int nbd_receive_structured_reply_chunk(QIOCha= nnel *ioc, chunk->handle =3D be64_to_cpu(chunk->handle); chunk->length =3D be32_to_cpu(chunk->length); + /* + * Because we use BLOCK_STATUS with REQ_ONE, and cap READ requests + * at 32M, no valid server should send us payload larger than + * this. Even if we stopped using REQ_ONE, sane servers will cap + * the number of extents they return for block status. + */ + if (chunk->length > NBD_MAX_BUFFER_SIZE + sizeof(NBDStructuredReadData= )) { + error_setg(errp, "server chunk %" PRIu32 " (%s) payload is too lon= g", + chunk->type, nbd_rep_lookup(chunk->type)); + return -EINVAL; + } + return 0; } --=20 2.40.1