From patchwork Wed Jul 1 19:39:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 11637135 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 96D616C1 for ; Wed, 1 Jul 2020 19:41:32 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6D4CF20760 for ; Wed, 1 Jul 2020 19:41:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Bdntr3no" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D4CF20760 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:46230 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jqibr-0004xW-ND for patchwork-qemu-devel@patchwork.kernel.org; Wed, 01 Jul 2020 15:41:31 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44270) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jqib5-0003qp-Gc for qemu-devel@nongnu.org; Wed, 01 Jul 2020 15:40:43 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:36255 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jqib2-00031Y-33 for qemu-devel@nongnu.org; Wed, 01 Jul 2020 15:40:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593632435; 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=Pa5Rcf0eJpre7pBAFVZnAHs+y14JK47+IjMdQfGsueQ=; b=Bdntr3noaZ8Tk4yZeJ3q7YY0hl47VKvrwRtL1CoV5HJWlcS5mDWcZFxx7U95Da/npfUcf9 edCpV4MPV84lpcwMjLM+PlOV8paQAVK3nB2Bc2DL2kkzQLyBvOmr3nzDZ4m3zbcMkmtRjs hZvCdzlJXJfHExLsLOREOsvIm/n58aw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-22-rt-QfN5cNI-Khk78V-ZKpQ-1; Wed, 01 Jul 2020 15:40:30 -0400 X-MC-Unique: rt-QfN5cNI-Khk78V-ZKpQ-1 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 1123D18FE860; Wed, 1 Jul 2020 19:40:30 +0000 (UTC) Received: from thinkpad.redhat.com (ovpn-112-51.ams2.redhat.com [10.36.112.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6FDD717D8F; Wed, 1 Jul 2020 19:40:16 +0000 (UTC) From: Laurent Vivier To: qemu-devel@nongnu.org Subject: [PATCH v3 2/2] net: detect errors from probing vnet hdr flag for TAP devices Date: Wed, 1 Jul 2020 21:39:51 +0200 Message-Id: <20200701193951.36248-3-lvivier@redhat.com> In-Reply-To: <20200701193951.36248-1-lvivier@redhat.com> References: <20200701193951.36248-1-lvivier@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=lvivier@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=205.139.110.61; envelope-from=lvivier@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/01 01:05:53 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laurent Vivier , =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Stefan Weil , Jason Wang , Markus Armbruster , "Dr . David Alan Gilbert" , Gerd Hoffmann , Paolo Bonzini , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: "Daniel P. Berrange" When QEMU sets up a tap based network device backend, it mostly ignores errors reported from various ioctl() calls it makes, assuming the TAP file descriptor is valid. This assumption can easily be violated when the user is passing in a pre-opened file descriptor. At best, the ioctls may fail with a -EBADF, but if the user passes in a bogus FD number that happens to clash with a FD number that QEMU has opened internally for another reason, a wide variety of errnos may result, as the TUNGETIFF ioctl number may map to a completely different command on a different type of file. By ignoring all these errors, QEMU sets up a zombie network backend that will never pass any data. Even worse, when QEMU shuts down, or that network backend is hot-removed, it will close this bogus file descriptor, which could belong to another QEMU device backend. There's no obvious guaranteed reliable way to detect that a FD genuinely is a TAP device, as opposed to a UNIX socket, or pipe, or something else. Checking the errno from probing vnet hdr flag though, does catch the big common cases. ie calling TUNGETIFF will return EBADF for an invalid FD, and ENOTTY when FD is a UNIX socket, or pipe which catches accidental collisions with FDs used for stdio, or monitor socket. Previously the example below where bogus fd 9 collides with the FD used for the chardev saw: $ ./x86_64-softmmu/qemu-system-x86_64 -netdev tap,id=hostnet0,fd=9 \ -chardev socket,id=charchannel0,path=/tmp/qga,server,nowait \ -monitor stdio -vnc :0 qemu-system-x86_64: -netdev tap,id=hostnet0,fd=9: TUNGETIFF ioctl() failed: Inappropriate ioctl for device TUNSETOFFLOAD ioctl() failed: Bad address QEMU 2.9.1 monitor - type 'help' for more information (qemu) Warning: netdev hostnet0 has no peer which gives a running QEMU with a zombie network backend. With this change applied we get an error message and QEMU immediately exits before carrying on and making a bigger disaster: $ ./x86_64-softmmu/qemu-system-x86_64 -netdev tap,id=hostnet0,fd=9 \ -chardev socket,id=charchannel0,path=/tmp/qga,server,nowait \ -monitor stdio -vnc :0 qemu-system-x86_64: -netdev tap,id=hostnet0,vhost=on,fd=9: Unable to query TUNGETIFF on FD 9: Inappropriate ioctl for device Reported-by: Dr. David Alan Gilbert Signed-off-by: Daniel P. Berrange Tested-by: Dr. David Alan Gilbert Message-id: 20171027085548.3472-1-berrange@redhat.com [lv: to simplify, don't check on EINVAL with TUNGETIFF as it exists since v2.6.27] Signed-off-by: Laurent Vivier Reviewed-by: Philippe Mathieu-Daudé --- net/tap-bsd.c | 2 +- net/tap-linux.c | 8 +++++--- net/tap-solaris.c | 2 +- net/tap-stub.c | 2 +- net/tap.c | 25 ++++++++++++++++++++----- net/tap_int.h | 2 +- 6 files changed, 29 insertions(+), 12 deletions(-) diff --git a/net/tap-bsd.c b/net/tap-bsd.c index a5c3707f806d..77aaf674b19d 100644 --- a/net/tap-bsd.c +++ b/net/tap-bsd.c @@ -211,7 +211,7 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp) { } -int tap_probe_vnet_hdr(int fd) +int tap_probe_vnet_hdr(int fd, Error **errp) { return 0; } diff --git a/net/tap-linux.c b/net/tap-linux.c index e0dd442ee34f..b0635e9e32ce 100644 --- a/net/tap-linux.c +++ b/net/tap-linux.c @@ -147,13 +147,15 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp) } } -int tap_probe_vnet_hdr(int fd) +int tap_probe_vnet_hdr(int fd, Error **errp) { struct ifreq ifr; if (ioctl(fd, TUNGETIFF, &ifr) != 0) { - error_report("TUNGETIFF ioctl() failed: %s", strerror(errno)); - return 0; + /* TUNGETIFF is available since kernel v2.6.27 */ + error_setg_errno(errp, errno, + "Unable to query TUNGETIFF on FD %d", fd); + return -1; } return ifr.ifr_flags & IFF_VNET_HDR; diff --git a/net/tap-solaris.c b/net/tap-solaris.c index 4725d2314eef..ae2ba6828415 100644 --- a/net/tap-solaris.c +++ b/net/tap-solaris.c @@ -206,7 +206,7 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp) { } -int tap_probe_vnet_hdr(int fd) +int tap_probe_vnet_hdr(int fd, Error **errp) { return 0; } diff --git a/net/tap-stub.c b/net/tap-stub.c index a9ab8f829362..de525a2e69d4 100644 --- a/net/tap-stub.c +++ b/net/tap-stub.c @@ -37,7 +37,7 @@ void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp) { } -int tap_probe_vnet_hdr(int fd) +int tap_probe_vnet_hdr(int fd, Error **errp) { return 0; } diff --git a/net/tap.c b/net/tap.c index fb04c9044ce2..208d9c0f8d35 100644 --- a/net/tap.c +++ b/net/tap.c @@ -597,7 +597,11 @@ int net_init_bridge(const Netdev *netdev, const char *name, } qemu_set_nonblock(fd); - vnet_hdr = tap_probe_vnet_hdr(fd); + vnet_hdr = tap_probe_vnet_hdr(fd, errp); + if (vnet_hdr < 0) { + close(fd); + return -1; + } s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr); snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s,br=%s", helper, @@ -803,7 +807,11 @@ int net_init_tap(const Netdev *netdev, const char *name, return -1; } - vnet_hdr = tap_probe_vnet_hdr(fd); + vnet_hdr = tap_probe_vnet_hdr(fd, errp); + if (vnet_hdr < 0) { + close(fd); + return -1; + } net_init_tap_one(tap, peer, "tap", name, NULL, script, downscript, @@ -856,8 +864,11 @@ int net_init_tap(const Netdev *netdev, const char *name, } if (i == 0) { - vnet_hdr = tap_probe_vnet_hdr(fd); - } else if (vnet_hdr != tap_probe_vnet_hdr(fd)) { + vnet_hdr = tap_probe_vnet_hdr(fd, errp); + if (vnet_hdr < 0) { + goto free_fail; + } + } else if (vnet_hdr != tap_probe_vnet_hdr(fd, NULL)) { error_setg(errp, "vnet_hdr not consistent across given tap fds"); ret = -1; @@ -902,7 +913,11 @@ free_fail: } qemu_set_nonblock(fd); - vnet_hdr = tap_probe_vnet_hdr(fd); + vnet_hdr = tap_probe_vnet_hdr(fd, errp); + if (vnet_hdr < 0) { + close(fd); + return -1; + } net_init_tap_one(tap, peer, "bridge", name, ifname, script, downscript, vhostfdname, diff --git a/net/tap_int.h b/net/tap_int.h index e3194b23f47d..225a49ea4843 100644 --- a/net/tap_int.h +++ b/net/tap_int.h @@ -34,7 +34,7 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr, ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen); void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp); -int tap_probe_vnet_hdr(int fd); +int tap_probe_vnet_hdr(int fd, Error **errp); int tap_probe_vnet_hdr_len(int fd, int len); int tap_probe_has_ufo(int fd); void tap_fd_set_offload(int fd, int csum, int tso4, int tso6, int ecn, int ufo);