From nobody Tue Feb 10 01:34:32 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 1638573830056712.9531354920805; Fri, 3 Dec 2021 15:23:50 -0800 (PST) Received: from localhost ([::1]:35910 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mtHu9-0003WV-0P for importer@patchew.org; Fri, 03 Dec 2021 18:23:49 -0500 Received: from eggs.gnu.org ([209.51.188.92]:37468) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mtHmi-0007J2-Bk for qemu-devel@nongnu.org; Fri, 03 Dec 2021 18:16:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:50929) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mtHme-00034h-BD for qemu-devel@nongnu.org; Fri, 03 Dec 2021 18:16:06 -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-489-kMdgzBqtP7SN3waLOsfHhA-1; Fri, 03 Dec 2021 18:16:00 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7AABB100CCC6; Fri, 3 Dec 2021 23:15:59 +0000 (UTC) Received: from blue.redhat.com (unknown [10.2.16.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id 60D205D9D5; Fri, 3 Dec 2021 23:15:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1638573363; 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=ReflyIVyVVxgUfE8lnp73Rx1x6HoY9UGsRIRe/TvEe4=; b=iLS5hZipxBiwYtwKSwaImNwXuP8Mv6+DlK+3kpkYiZSyNbM9wYzldsgiIeY0uQOMJkI9gA hhEUKPj77dFt16OeZorP5XGdLcjgT8R5aHclAfTcqZes7Gor2QnBdmc4x5nBwlEkDQ+U92 XaYedIxBQlZkUM900ndtEXRNYVkdwKw= X-MC-Unique: kMdgzBqtP7SN3waLOsfHhA-1 From: Eric Blake To: qemu-devel@nongnu.org Subject: [PATCH 03/14] qemu-io: Allow larger write zeroes under no fallback Date: Fri, 3 Dec 2021 17:15:28 -0600 Message-Id: <20211203231539.3900865-4-eblake@redhat.com> In-Reply-To: <20211203231539.3900865-1-eblake@redhat.com> References: <20211203231307.wmtbw7r72tyzkkax@redhat.com> <20211203231539.3900865-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.717, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , vsementsov@virtuozzo.com, qemu-block@nongnu.org, nbd@other.debian.org, nsoffer@redhat.com, Hanna Reitz , libguestfs@redhat.com 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: 1638573831731100003 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 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 2.33.1