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 lists1p.gnu.org (lists1p.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 2CCB1C79F83 for ; Fri, 4 Sep 2026 11:01:09 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x2ReC-0004XR-IX; Fri, 04 Sep 2026 06:59:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x2ReB-0004Wi-3l for qemu-devel@nongnu.org; Fri, 04 Sep 2026 06:59:51 -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 1x2Re9-0007bp-Dv for qemu-devel@nongnu.org; Fri, 04 Sep 2026 06:59:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788519588; 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=ASYz6iulwfFvbmqEMTfqctGI341Oz4dZKbFqz9gwcLM=; b=NtjT7ks+NdCL0Xq5X5Btm3+0uLbKx3YMEuSw8qKgYKCGJFdVT5UbrXmQ6hc5rgK8ut1t+j 3CJsciI7Xjw/Dasn6fTXzZhwNZeBOsM2uadxlvl2eNLnDKisfMkcdrKqOMXtK8PxhiGwi1 C0ZhSyAN+rxXdAh7qtpWOP8dOmGHcmQ= Received: from mx-prod-mc-01.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-453--ocZRgAROkK6YxCD7NltTg-1; Fri, 04 Sep 2026 06:59:44 -0400 X-MC-Unique: -ocZRgAROkK6YxCD7NltTg-1 X-Mimecast-MFC-AGG-ID: -ocZRgAROkK6YxCD7NltTg_1788519583 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4F222195396B; Fri, 4 Sep 2026 10:59:43 +0000 (UTC) Received: from berrange.csb (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 22F6818005BD; Fri, 4 Sep 2026 10:59:40 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= , Pierrick Bouvier , devel@lists.libvirt.org, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Paolo Bonzini , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , qemu-stable@nongnu.org, "Denis V. Lunev" Subject: [PULL 04/13] io/channel-socket: do not treat a zero length write as an error Date: Fri, 4 Sep 2026 11:59:20 +0100 Message-ID: <20260904105929.3450663-5-berrange@redhat.com> In-Reply-To: <20260904105929.3450663-1-berrange@redhat.com> References: <20260904105929.3450663-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 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, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Denis V. Lunev qio_channel_socket_writev() checks "ret <= 0" after sendmsg(). A zero length iovec is written successfully and returns 0, so the success falls into the errno switch, which acts on whatever the last failing syscall left in errno. A stale EAGAIN turns it into QIO_CHANNEL_ERR_BLOCK with errp untouched, and a caller which treats every negative return as fatal then passes a NULL Error to error_get_pretty(). The websocket handshake does exactly that, so an unauthenticated client crashes QEMU during the greeting. Returning 0 is safe for callers which loop until everything is written. qio_channel_writev_full_all() has no zero progress guard, but iov_copy() yields no entries for a zero length write, so that loop is never entered. A connected stream socket returns 0 only when there is nothing to send. The WIN32 implementation in the same file uses "ret < 0". Fixes: CVE-2026-84788 Fixes: 559607ea173a ("io: add QIOChannelSocket class") Cc: qemu-stable@nongnu.org Cc: Daniel P. Berrangé Cc: Marc-André Lureau Reviewed-by: Daniel P. Berrangé Reviewed-by: Marc-André Lureau Signed-off-by: Denis V. Lunev Signed-off-by: Daniel P. Berrangé --- io/channel-socket.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/io/channel-socket.c b/io/channel-socket.c index 12773b832c..7920cee639 100644 --- a/io/channel-socket.c +++ b/io/channel-socket.c @@ -667,7 +667,7 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc, retry: ret = sendmsg(sioc->fd, &msg, sflags); - if (ret <= 0) { + if (ret < 0) { switch (errno) { case EAGAIN: return QIO_CHANNEL_ERR_BLOCK; -- 2.55.0