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,URIBL_BLOCKED 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 A93EBC43441 for ; Sun, 11 Nov 2018 20:15:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 78B1B2080D for ; Sun, 11 Nov 2018 20:15:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 78B1B2080D 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 S1731808AbeKLGFN (ORCPT ); Mon, 12 Nov 2018 01:05:13 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:53050 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731042AbeKLGFN (ORCPT ); Mon, 12 Nov 2018 01:05:13 -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 1gLvsx-0000oJ-03; Sun, 11 Nov 2018 19:59:07 +0000 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gLvsU-0001dj-GD; Sun, 11 Nov 2018 19:58:38 +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, "Jann Horn" , "Pablo Neira Ayuso" Date: Sun, 11 Nov 2018 19:49:05 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 200/366] netfilter: nf_log: don't hold nf_log_mutex during user access 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: Jann Horn commit ce00bf07cc95a57cd20b208e02b3c2604e532ae8 upstream. The old code would indefinitely block other users of nf_log_mutex if a userspace access in proc_dostring() blocked e.g. due to a userfaultfd region. Fix it by moving proc_dostring() out of the locked region. This is a followup to commit 266d07cb1c9a ("netfilter: nf_log: fix sleeping function called from invalid context"), which changed this code from using rcu_read_lock() to taking nf_log_mutex. Fixes: 266d07cb1c9a ("netfilter: nf_log: fix sleeping function calle[...]") Signed-off-by: Jann Horn Signed-off-by: Pablo Neira Ayuso [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- net/netfilter/nf_log.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/net/netfilter/nf_log.c +++ b/net/netfilter/nf_log.c @@ -273,15 +273,18 @@ static int nf_log_proc_dostring(struct c rcu_assign_pointer(net->nf.nf_loggers[tindex], logger); mutex_unlock(&nf_log_mutex); } else { + struct ctl_table tmp = *table; + + tmp.data = buf; mutex_lock(&nf_log_mutex); logger = rcu_dereference_protected(net->nf.nf_loggers[tindex], lockdep_is_held(&nf_log_mutex)); if (!logger) - table->data = "NONE"; + strlcpy(buf, "NONE", sizeof(buf)); else - table->data = logger->name; - r = proc_dostring(table, write, buffer, lenp, ppos); + strlcpy(buf, logger->name, sizeof(buf)); mutex_unlock(&nf_log_mutex); + r = proc_dostring(&tmp, write, buffer, lenp, ppos); } return r;