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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52924 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jquQB-0006Zh-Ix for qemu-devel@archiver.kernel.org; Thu, 02 Jul 2020 04:18:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59978) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jquPM-0005qx-Sv for qemu-devel@nongnu.org; Thu, 02 Jul 2020 04:17:24 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:54839 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 1jquPK-0008LR-He for qemu-devel@nongnu.org; Thu, 02 Jul 2020 04:17:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593677841; 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:autocrypt:autocrypt; bh=bAlTLda27iLxPE/4b0m9EX0wOogMG3rJLcGJQYVv2hA=; b=Utns+UGU91Sg2uWwIJ3a1h2bThj5KGE2pLwYd7t9yla7vhHR+73MYYEJy9f0jd90hcs1/5 yqS0ZCa7FHMkVr8IJ2nFCGKL5ydo6czd6HU0d9PBfMOyKMuxC4+ubv69dlboUKb4qrZuaf 4zvokXKeRaV9z2vaCL7zNyOyiRKuz1I= 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-6-16Zfr7GVMvWOGNzihtKm_Q-1; Thu, 02 Jul 2020 04:17:19 -0400 X-MC-Unique: 16Zfr7GVMvWOGNzihtKm_Q-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 5EBCA800C60; Thu, 2 Jul 2020 08:17:18 +0000 (UTC) Received: from [10.36.112.51] (ovpn-112-51.ams2.redhat.com [10.36.112.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id A726A5DD61; Thu, 2 Jul 2020 08:17:13 +0000 (UTC) Subject: Re: [PATCH v3 1/2] net: tap: check if the file descriptor is valid before using it To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <20200701193951.36248-1-lvivier@redhat.com> <20200701193951.36248-2-lvivier@redhat.com> <48ef599b-20b8-0cfa-4c73-548f1f9bebee@redhat.com> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <48ef599b-20b8-0cfa-4c73-548f1f9bebee@redhat.com> Content-Language: en-US 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 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit 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 = 2020/07/02 03:42:59 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: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Stefan Weil , Jason Wang , Markus Armbruster , Gerd Hoffmann , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 02/07/2020 10:00, Philippe Mathieu-Daudé wrote: > On 7/1/20 9:39 PM, Laurent Vivier wrote: >> qemu_set_nonblock() checks that the file descriptor can be used and, if >> not, crashes QEMU. An assert() is used for that. The use of assert() is >> used to detect programming error and the coredump will allow to debug >> the problem. >> >> But in the case of the tap device, this assert() can be triggered by >> a misconfiguration by the user. At startup, it's not a real problem, but it >> can also happen during the hot-plug of a new device, and here it's a >> problem because we can crash a perfectly healthy system. >> >> For instance: >> # ip link add link virbr0 name macvtap0 type macvtap mode bridge >> # ip link set macvtap0 up >> # TAP=/dev/tap$(ip -o link show macvtap0 | cut -d: -f1) >> # qemu-system-x86_64 -machine q35 -device pcie-root-port,id=pcie-root-port-0 -monitor stdio 9<> $TAP >> (qemu) netdev_add type=tap,id=hostnet0,vhost=on,fd=9 >> (qemu) device_add driver=virtio-net-pci,netdev=hostnet0,id=net0,bus=pcie-root-port-0 >> (qemu) device_del net0 >> (qemu) netdev_del hostnet0 >> (qemu) netdev_add type=tap,id=hostnet1,vhost=on,fd=9 >> qemu-system-x86_64: .../util/oslib-posix.c:247: qemu_set_nonblock: Assertion `f != -1' failed. >> Aborted (core dumped) >> >> To avoid that, add a function, qemu_try_set_nonblock(), that allows to report the >> problem without crashing. >> >> Signed-off-by: Laurent Vivier >> --- >> include/qemu/sockets.h | 1 + >> net/tap.c | 16 +++++++++--- >> util/oslib-posix.c | 26 +++++++++++++------ >> util/oslib-win32.c | 57 ++++++++++++++++++++++++------------------ >> 4 files changed, 64 insertions(+), 36 deletions(-) >> >> diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h >> index 57cd049d6edd..7d1f8135767d 100644 >> --- a/include/qemu/sockets.h >> +++ b/include/qemu/sockets.h >> @@ -18,6 +18,7 @@ int qemu_accept(int s, struct sockaddr *addr, socklen_t *addrlen); >> int socket_set_cork(int fd, int v); >> int socket_set_nodelay(int fd); >> void qemu_set_block(int fd); >> +int qemu_try_set_nonblock(int fd); >> void qemu_set_nonblock(int fd); >> int socket_set_fast_reuse(int fd); >> >> diff --git a/net/tap.c b/net/tap.c >> index 6207f61f84ab..fb04c9044ce2 100644 >> --- a/net/tap.c >> +++ b/net/tap.c >> @@ -766,6 +766,7 @@ int net_init_tap(const Netdev *netdev, const char *name, >> Error *err = NULL; >> const char *vhostfdname; >> char ifname[128]; >> + int ret = 0; > > No need to zero-initialize. > > Otherwise: > Reviewed-by: Philippe Mathieu-Daudé > I would agree with you but gcc doesn't: net/tap.c:769:9: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized] 769 | int ret; | ^~~ if nfds == 0, we don't enter in the loop and ret is never set. Thanks, Laurent