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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B71F8C4724C for ; Fri, 1 May 2020 19:18:51 +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 7E8072166E for ; Fri, 1 May 2020 19:18:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XXMrURoR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E8072166E 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+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:43100 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jUbBS-0002yB-Hs for qemu-devel@archiver.kernel.org; Fri, 01 May 2020 15:18:50 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33404) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jUb87-0006eZ-T5 for qemu-devel@nongnu.org; Fri, 01 May 2020 15:15:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.90_1) (envelope-from ) id 1jUb86-00007s-3T for qemu-devel@nongnu.org; Fri, 01 May 2020 15:15:23 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:44819 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 1jUb85-00005h-LZ for qemu-devel@nongnu.org; Fri, 01 May 2020 15:15:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588360520; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a7tlgW/RV4oirjcdS6rirP8fOn1hpnptskhP1fFJ9kE=; b=XXMrURoRGSKNJwXcx+zg1qEPQVwsXD2lDMC/8NMuwHp2f42eai3EiHpfRCVhFk4t58Trdd Bz33EirmjXXivNaNq+5mFH/Uhn/Lfb0sHBO67x+DNW9PnJy9ZsqUW+KXqFloIOQjGSugVT h7rdegeUYiAfKMA1SCLNNCoQCkSbSgo= 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-460-7GzpNJYTNVys9wAnzSwwLA-1; Fri, 01 May 2020 15:15:15 -0400 X-MC-Unique: 7GzpNJYTNVys9wAnzSwwLA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F3BBBA0C06; Fri, 1 May 2020 19:15:14 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-112-191.ams2.redhat.com [10.36.112.191]) by smtp.corp.redhat.com (Postfix) with ESMTP id BE2641002382; Fri, 1 May 2020 19:15:13 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, yavrahami@paloaltonetworks.com, mszeredi@redhat.com, mreitz@redhat.com Subject: [PULL 2/6] virtiofsd: stay below fs.file-max sysctl value (CVE-2020-10717) Date: Fri, 1 May 2020 20:14:56 +0100 Message-Id: <20200501191500.126432-3-dgilbert@redhat.com> In-Reply-To: <20200501191500.126432-1-dgilbert@redhat.com> References: <20200501191500.126432-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=205.139.110.120; envelope-from=dgilbert@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/01 08:22:51 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Stefan Hajnoczi The system-wide fs.file-max sysctl value determines how many files can be open. It defaults to a value calculated based on the machine's RAM size. Previously virtiofsd would try to set RLIMIT_NOFILE to 1,000,000 and this allowed the FUSE client to exhaust the number of open files system-wide on Linux hosts with less than 10 GB of RAM! Take fs.file-max into account when choosing the default RLIMIT_NOFILE value. Fixes: CVE-2020-10717 Reported-by: Yuval Avrahami Signed-off-by: Stefan Hajnoczi Reviewed-by: Dr. David Alan Gilbert Message-Id: <20200501140644.220940-3-stefanha@redhat.com> Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/helper.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c index dc59f38af0..00a1ef666a 100644 --- a/tools/virtiofsd/helper.c +++ b/tools/virtiofsd/helper.c @@ -176,7 +176,8 @@ void fuse_cmdline_help(void) " default: no_xattr\n" " --rlimit-nofile=3D set maximum number of file de= scriptors\n" " (0 leaves rlimit unchanged)\n" - " default: 1,000,000 if the curre= nt rlimit is lower\n" + " default: min(1000000, fs.file-m= ax - 16384)\n" + " if the current rlimit = is lower\n" ); } =20 @@ -199,9 +200,32 @@ static int fuse_helper_opt_proc(void *data, const char= *arg, int key, =20 static unsigned long get_default_rlimit_nofile(void) { + g_autofree gchar *file_max_str =3D NULL; + const rlim_t reserved_fds =3D 16384; /* leave at least this many fds f= ree */ rlim_t max_fds =3D 1000000; /* our default RLIMIT_NOFILE target */ + rlim_t file_max; struct rlimit rlim; =20 + /* + * Reduce max_fds below the system-wide maximum, if necessary. This + * ensures there are fds available for other processes so we don't + * cause resource exhaustion. + */ + if (!g_file_get_contents("/proc/sys/fs/file-max", &file_max_str, + NULL, NULL)) { + fuse_log(FUSE_LOG_ERR, "can't read /proc/sys/fs/file-max\n"); + exit(1); + } + file_max =3D g_ascii_strtoull(file_max_str, NULL, 10); + if (file_max < 2 * reserved_fds) { + fuse_log(FUSE_LOG_ERR, + "The fs.file-max sysctl is too low (%lu) to allow a " + "reasonable number of open files.\n", + (unsigned long)file_max); + exit(1); + } + max_fds =3D MIN(file_max - reserved_fds, max_fds); + if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) { fuse_log(FUSE_LOG_ERR, "getrlimit(RLIMIT_NOFILE): %m\n"); exit(1); --=20 2.26.2