From nobody Wed Nov 5 13:42:55 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1498214151598518.0809392268251; Fri, 23 Jun 2017 03:35:51 -0700 (PDT) Received: from localhost ([::1]:34716 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dOLwM-00019Q-1N for importer@patchew.org; Fri, 23 Jun 2017 06:35:50 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60491) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dOLsN-0006J5-9e for qemu-devel@nongnu.org; Fri, 23 Jun 2017 06:31:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dOLsK-0001SY-4b for qemu-devel@nongnu.org; Fri, 23 Jun 2017 06:31:43 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:49514) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dOLsJ-0001SN-QH for qemu-devel@nongnu.org; Fri, 23 Jun 2017 06:31:40 -0400 Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id v5NAVcVP027026 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 23 Jun 2017 10:31:38 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id v5NAVc4Z013115 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 23 Jun 2017 10:31:38 GMT Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by aserv0121.oracle.com (8.13.8/8.13.8) with ESMTP id v5NAVZLa009847; Fri, 23 Jun 2017 10:31:36 GMT Received: from abi.no.oracle.com (/10.172.144.123) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 23 Jun 2017 03:31:35 -0700 From: Knut Omang To: "Daniel P . Berrange" , Gerd Hoffmann , Paolo Bonzini Date: Fri, 23 Jun 2017 12:31:08 +0200 Message-Id: <51d7f54d100e9dedecf6dc65691ca65adfc8394f.1498213152.git-series.knut.omang@oracle.com> X-Mailer: git-send-email 2.9.4 In-Reply-To: References: X-Source-IP: aserv0022.oracle.com [141.146.126.234] X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] [fuzzy] X-Received-From: 141.146.126.69 Subject: [Qemu-devel] [PATCH v4 4/4] sockets: Handle race condition between binds to the same port 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: Knut Omang , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" If an offset of ports is specified to the inet_listen_saddr function(), and two or more processes tries to bind from these ports at the same time, occasionally more than one process may be able to bind to the same port. The condition is detected by listen() but too late to avoid a failure. This function is called by socket_listen() and used by all socket listening code in QEMU, so all cases where any form of dynamic port selection is used should be subject to this issue. Add code to close and re-establish the socket when this condition is observed, hiding the race condition from the user. This has been developed and tested by means of the test-listen unit test in the previous commit. Enable the test for make check now that it passes. Signed-off-by: Knut Omang Reviewed-by: Bhavesh Davda Reviewed-by: Yuval Shaia Reviewed-by: Girish Moodalbail --- tests/Makefile.include | 2 +- util/qemu-sockets.c | 68 ++++++++++++++++++++++++++++++++----------- 2 files changed, 53 insertions(+), 17 deletions(-) diff --git a/tests/Makefile.include b/tests/Makefile.include index 22bb97e..c38f94e 100644 --- a/tests/Makefile.include +++ b/tests/Makefile.include @@ -127,7 +127,7 @@ check-unit-y +=3D tests/test-bufferiszero$(EXESUF) gcov-files-check-bufferiszero-y =3D util/bufferiszero.c check-unit-y +=3D tests/test-uuid$(EXESUF) check-unit-y +=3D tests/ptimer-test$(EXESUF) -#check-unit-y +=3D tests/test-listen$(EXESUF) +check-unit-y +=3D tests/test-listen$(EXESUF) gcov-files-ptimer-test-y =3D hw/core/ptimer.c check-unit-y +=3D tests/test-qapi-util$(EXESUF) gcov-files-test-qapi-util-y =3D qapi/qapi-util.c diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 48b9319..7b118b4 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -201,6 +201,42 @@ static int try_bind(int socket, InetSocketAddress *sad= dr, struct addrinfo *e) #endif } =20 +static int try_bind_listen(int *socket, InetSocketAddress *saddr, + struct addrinfo *e, int port, Error **errp) +{ + int s =3D *socket; + int ret; + + inet_setport(e, port); + ret =3D try_bind(s, saddr, e); + if (ret) { + if (errno !=3D EADDRINUSE) { + error_setg_errno(errp, errno, "Failed to bind socket"); + } + return errno; + } + if (listen(s, 1) =3D=3D 0) { + return 0; + } + if (errno =3D=3D EADDRINUSE) { + /* We got to bind the socket to a port but someone else managed + * to bind to the same port and beat us to listen on it! + * Recreate the socket and return EADDRINUSE to preserve the + * expected state by the caller: + */ + closesocket(s); + s =3D create_fast_reuse_socket(e, errp); + if (s < 0) { + return errno; + } + *socket =3D s; + errno =3D EADDRINUSE; + return errno; + } + error_setg_errno(errp, errno, "Failed to listen on socket"); + return errno; +} + static int inet_listen_saddr(InetSocketAddress *saddr, int port_offset, bool update_addr, @@ -210,7 +246,9 @@ static int inet_listen_saddr(InetSocketAddress *saddr, char port[33]; char uaddr[INET6_ADDRSTRLEN+1]; char uport[33]; - int slisten, rc, port_min, port_max, p; + int rc, port_min, port_max, p; + int slisten =3D 0; + int saved_errno =3D 0; Error *err =3D NULL; =20 memset(&ai,0, sizeof(ai)); @@ -276,28 +314,26 @@ static int inet_listen_saddr(InetSocketAddress *saddr, port_min =3D inet_getport(e); port_max =3D saddr->has_to ? saddr->to + port_offset : port_min; for (p =3D port_min; p <=3D port_max; p++) { - inet_setport(e, p); - if (try_bind(slisten, saddr, e) >=3D 0) { - goto listen; - } - if (p =3D=3D port_max) { - if (!e->ai_next) { - error_setg_errno(errp, errno, "Failed to bind socket"); - } + int eno =3D try_bind_listen(&slisten, saddr, e, p, &err); + if (!eno) { + goto listen_ok; + } else if (eno !=3D EADDRINUSE) { + goto listen_failed; } } + } + error_setg_errno(errp, errno, "Failed to find available port"); + +listen_failed: + saved_errno =3D errno; + if (slisten >=3D 0) { closesocket(slisten); } freeaddrinfo(res); + errno =3D saved_errno; return -1; =20 -listen: - if (listen(slisten,1) !=3D 0) { - error_setg_errno(errp, errno, "Failed to listen on socket"); - closesocket(slisten); - freeaddrinfo(res); - return -1; - } +listen_ok: if (update_addr) { g_free(saddr->host); saddr->host =3D g_strdup(uaddr); --=20 git-series 0.9.1