From patchwork Fri Oct 27 08:55:48 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= X-Patchwork-Id: 10029443 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 116CF60249 for ; Fri, 27 Oct 2017 08:56:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 03E6428EC6 for ; Fri, 27 Oct 2017 08:56:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EB48528F56; Fri, 27 Oct 2017 08:56:40 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.3 required=2.0 tests=BAYES_00,FUZZY_AMBIEN, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 5A48328EC6 for ; Fri, 27 Oct 2017 08:56:40 +0000 (UTC) Received: from localhost ([::1]:56291 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e80RS-0002cT-MA for patchwork-qemu-devel@patchwork.kernel.org; Fri, 27 Oct 2017 04:56:38 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58466) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e80Qq-0002cL-3y for qemu-devel@nongnu.org; Fri, 27 Oct 2017 04:56:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e80Ql-00087U-4B for qemu-devel@nongnu.org; Fri, 27 Oct 2017 04:56:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60262) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e80Qk-00083Y-SD for qemu-devel@nongnu.org; Fri, 27 Oct 2017 04:55:55 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 6A95FA7E5 for ; Fri, 27 Oct 2017 08:55:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6A95FA7E5 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=berrange@redhat.com Received: from localhost.localdomain.com (unknown [10.40.205.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 31CD860619; Fri, 27 Oct 2017 08:55:51 +0000 (UTC) From: "Daniel P. Berrange" To: qemu-devel@nongnu.org Date: Fri, 27 Oct 2017 09:55:48 +0100 Message-Id: <20171027085548.3472-1-berrange@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 27 Oct 2017 08:55:53 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH] net: detect errors from probing vnet hdr flag for TAP devices X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jason Wang , "Dr . David Alan Gilbert" Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP 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 --- net/tap-bsd.c | 2 +- net/tap-linux.c | 12 +++++++++--- net/tap-solaris.c | 2 +- net/tap-stub.c | 2 +- net/tap.c | 25 ++++++++++++++++++++----- net/tap_int.h | 2 +- 6 files changed, 33 insertions(+), 12 deletions(-) diff --git a/net/tap-bsd.c b/net/tap-bsd.c index 6c9692263d..4f1d633b08 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 535b1ddb61..de74928407 100644 --- a/net/tap-linux.c +++ b/net/tap-linux.c @@ -147,13 +147,19 @@ 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; + /* Kernel pre-dates TUNGETIFF support */ + if (errno == -EINVAL) { + return 0; + } else { + 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 a2a92356c1..3437838a92 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 a9ab8f8293..de525a2e69 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 979e622e60..763fd2d9b2 100644 --- a/net/tap.c +++ b/net/tap.c @@ -592,7 +592,11 @@ int net_init_bridge(const Netdev *netdev, const char *name, } fcntl(fd, F_SETFL, O_NONBLOCK); - 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, @@ -779,7 +783,11 @@ int net_init_tap(const Netdev *netdev, const char *name, fcntl(fd, F_SETFL, O_NONBLOCK); - 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, @@ -825,8 +833,11 @@ int net_init_tap(const Netdev *netdev, const char *name, fcntl(fd, F_SETFL, O_NONBLOCK); 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"); goto free_fail; @@ -870,7 +881,11 @@ free_fail: } fcntl(fd, F_SETFL, O_NONBLOCK); - 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 ae6888f74a..0d13768615 100644 --- a/net/tap_int.h +++ b/net/tap_int.h @@ -35,7 +35,7 @@ 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);