From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Pablo Neira Ayuso Subject: [PATCH 4.4 46/47] netfilter: nf_log: dont hold nf_log_mutex during user access Date: Tue, 10 Jul 2018 20:25:10 +0200 Message-Id: <20180710182339.143507542@linuxfoundation.org> In-Reply-To: <20180710182337.047502999@linuxfoundation.org> References: <20180710182337.047502999@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.4-stable 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 Signed-off-by: Greg Kroah-Hartman --- 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 @@ -422,14 +422,17 @@ 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 = nft_log_dereference(net->nf.nf_loggers[tindex]); 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;