From nobody Sun Feb 8 20:08:48 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; 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=fail(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1646705270100868.373478192515; Mon, 7 Mar 2022 18:07:50 -0800 (PST) Received: from localhost ([::1]:45560 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nRPGO-0005Zj-V6 for importer@patchew.org; Mon, 07 Mar 2022 21:07:48 -0500 Received: from eggs.gnu.org ([209.51.188.92]:53140) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nROu8-0000D7-0s for qemu-devel@nongnu.org; Mon, 07 Mar 2022 20:44:48 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:38954) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nROu6-0006QN-2U for qemu-devel@nongnu.org; Mon, 07 Mar 2022 20:44:47 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-53-u3cpwcaTPnCO6858HwMNlg-1; Mon, 07 Mar 2022 20:44:42 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5AEF12F35; Tue, 8 Mar 2022 01:44:41 +0000 (UTC) Received: from blue.redhat.com (unknown [10.2.16.5]) by smtp.corp.redhat.com (Postfix) with ESMTP id 928BE5E480; Tue, 8 Mar 2022 01:44:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646703885; 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=7p7pFOdgSqGhud7GsIP/QghHbL0OwMTKZyDUpnqoPrk=; b=eWCkDca2huFoI1bKrMIxoUfwG+RiR1WBqzRZRxsucQ9dCcJoV10extTsDkyuTGwNRpIE9Q ni9PID2S8yQPJB4hNVH2WZz3fl/mx9XnEre5CqYqsQ3bq/PZIuxCnpvLi2gfCpRtlpZ+0S fadwM6y8KT4HkpqELdfcN2asX1qg0Dc= X-MC-Unique: u3cpwcaTPnCO6858HwMNlg-1 From: Eric Blake To: qemu-devel@nongnu.org Subject: [PULL 15/15] qemu-io: Allow larger write zeroes under no fallback Date: Mon, 7 Mar 2022 19:44:19 -0600 Message-Id: <20220308014419.3056549-16-eblake@redhat.com> In-Reply-To: <20220308014419.3056549-1-eblake@redhat.com> References: <20220308014419.3056549-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable 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=-0.082, 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: , Cc: Kevin Wolf , Hanna Reitz , Vladimir Sementsov-Ogievskiy , "open list:Block layer core" Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1646705272070100001 Content-Type: text/plain; charset="utf-8" When writing zeroes can fall back to a slow write, permitting an overly large request can become an amplification denial of service attack in triggering a large amount of work from a small request. But the whole point of the no fallback flag is to quickly determine if writing an entire device to zero can be done quickly (such as when it is already known that the device started with zero contents); in those cases, artificially capping things at 2G in qemu-io itself doesn't help us. Signed-off-by: Eric Blake Message-Id: <20211203231539.3900865-4-eblake@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy --- qemu-io-cmds.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c index 954955c12fb9..45a957093369 100644 --- a/qemu-io-cmds.c +++ b/qemu-io-cmds.c @@ -603,10 +603,6 @@ static int do_co_pwrite_zeroes(BlockBackend *blk, int6= 4_t offset, .done =3D false, }; - if (bytes > INT_MAX) { - return -ERANGE; - } - co =3D qemu_coroutine_create(co_pwrite_zeroes_entry, &data); bdrv_coroutine_enter(blk_bs(blk), co); while (!data.done) { @@ -1160,8 +1156,9 @@ static int write_f(BlockBackend *blk, int argc, char = **argv) if (count < 0) { print_cvtnum_err(count, argv[optind]); return count; - } else if (count > BDRV_REQUEST_MAX_BYTES) { - printf("length cannot exceed %" PRIu64 ", given %s\n", + } else if (count > BDRV_REQUEST_MAX_BYTES && + !(flags & BDRV_REQ_NO_FALLBACK)) { + printf("length cannot exceed %" PRIu64 " without -n, given %s\n", (uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]); return -EINVAL; } --=20 2.35.1