From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 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: Subject: [PATCH 3.16 200/366] netfilter: nf_log: don't hold nf_log_mutex during user access In-Reply-To: Sender: stable-owner@vger.kernel.org List-ID: 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;