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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 705E9C43441 for ; Sun, 11 Nov 2018 20:24:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3BB1020818 for ; Sun, 11 Nov 2018 20:24:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3BB1020818 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731089AbeKLGOH (ORCPT ); Mon, 12 Nov 2018 01:14:07 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51090 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730695AbeKLFsa (ORCPT ); Mon, 12 Nov 2018 00:48:30 -0500 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gLvsq-0000oF-Ld; Sun, 11 Nov 2018 19:59:00 +0000 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gLvsW-0001k1-VY; Sun, 11 Nov 2018 19:58:40 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David S. Miller" , "syzbot" , "Eric Biggers" Date: Sun, 11 Nov 2018 19:49:05 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 263/366] KEYS: DNS: fix parsing multiple options In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.61-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit c604cb767049b78b3075497b80ebb8fd530ea2cc upstream. My recent fix for dns_resolver_preparse() printing very long strings was incomplete, as shown by syzbot which still managed to hit the WARN_ONCE() in set_precision() by adding a crafted "dns_resolver" key: precision 50001 too large WARNING: CPU: 7 PID: 864 at lib/vsprintf.c:2164 vsnprintf+0x48a/0x5a0 The bug this time isn't just a printing bug, but also a logical error when multiple options ("#"-separated strings) are given in the key payload. Specifically, when separating an option string into name and value, if there is no value then the name is incorrectly considered to end at the end of the key payload, rather than the end of the current option. This bypasses validation of the option length, and also means that specifying multiple options is broken -- which presumably has gone unnoticed as there is currently only one valid option anyway. A similar problem also applied to option values, as the kstrtoul() when parsing the "dnserror" option will read past the end of the current option and into the next option. Fix these bugs by correctly computing the length of the option name and by copying the option value, null-terminated, into a temporary buffer. Reproducer for the WARN_ONCE() that syzbot hit: perl -e 'print "#A#", "\0" x 50000' | keyctl padd dns_resolver desc @s Reproducer for "dnserror" option being parsed incorrectly (expected behavior is to fail when seeing the unknown option "foo", actual behavior was to read the dnserror value as "1#foo" and fail there): perl -e 'print "#dnserror=1#foo\0"' | keyctl padd dns_resolver desc @s Reported-by: syzbot Fixes: 4a2d789267e0 ("DNS: If the DNS server returns an error, allow that to be cached [ver #2]") Signed-off-by: Eric Biggers Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/dns_resolver/dns_key.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) --- a/net/dns_resolver/dns_key.c +++ b/net/dns_resolver/dns_key.c @@ -89,35 +89,39 @@ dns_resolver_instantiate(struct key *key opt++; kdebug("options: '%s'", opt); do { + int opt_len, opt_nlen; const char *eq; - int opt_len, opt_nlen, opt_vlen, tmp; + char optval[128]; next_opt = memchr(opt, '#', end - opt) ?: end; opt_len = next_opt - opt; - if (opt_len <= 0 || opt_len > 128) { + if (opt_len <= 0 || opt_len > sizeof(optval)) { pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n", opt_len); return -EINVAL; } - eq = memchr(opt, '=', opt_len) ?: end; - opt_nlen = eq - opt; - eq++; - opt_vlen = next_opt - eq; /* will be -1 if no value */ - - tmp = opt_vlen >= 0 ? opt_vlen : 0; - kdebug("option '%*.*s' val '%*.*s'", - opt_nlen, opt_nlen, opt, tmp, tmp, eq); + eq = memchr(opt, '=', opt_len); + if (eq) { + opt_nlen = eq - opt; + eq++; + memcpy(optval, eq, next_opt - eq); + optval[next_opt - eq] = '\0'; + } else { + opt_nlen = opt_len; + optval[0] = '\0'; + } + + kdebug("option '%*.*s' val '%s'", + opt_nlen, opt_nlen, opt, optval); /* see if it's an error number representing a DNS error * that's to be recorded as the result in this key */ if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 && memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) { kdebug("dns error number option"); - if (opt_vlen <= 0) - goto bad_option_value; - ret = kstrtoul(eq, 10, &derrno); + ret = kstrtoul(optval, 10, &derrno); if (ret < 0) goto bad_option_value;