From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:37910 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936396AbdKPRtO (ORCPT ); Thu, 16 Nov 2017 12:49:14 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Willem de Bruijn , John Sperbeck , "David S. Miller" Subject: [PATCH 4.13 13/44] packet: avoid panic in packet_getsockopt() Date: Thu, 16 Nov 2017 18:42:37 +0100 Message-Id: <20171116172824.227625834@linuxfoundation.org> In-Reply-To: <20171116172823.336649076@linuxfoundation.org> References: <20171116172823.336649076@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 509c7a1ecc8601f94ffba8a00889fefb239c00c6 ] syzkaller got crashes in packet_getsockopt() processing PACKET_ROLLOVER_STATS command while another thread was managing to change po->rollover Using RCU will fix this bug. We might later add proper RCU annotations for sparse sake. In v2: I replaced kfree(rollover) in fanout_add() to kfree_rcu() variant, as spotted by John. Fixes: a9b6391814d5 ("packet: rollover statistics") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Cc: John Sperbeck Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/packet/af_packet.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1771,7 +1771,7 @@ static int fanout_add(struct sock *sk, u out: if (err && rollover) { - kfree(rollover); + kfree_rcu(rollover, rcu); po->rollover = NULL; } mutex_unlock(&fanout_mutex); @@ -1798,8 +1798,10 @@ static struct packet_fanout *fanout_rele else f = NULL; - if (po->rollover) + if (po->rollover) { kfree_rcu(po->rollover, rcu); + po->rollover = NULL; + } } mutex_unlock(&fanout_mutex); @@ -3853,6 +3855,7 @@ static int packet_getsockopt(struct sock void *data = &val; union tpacket_stats_u st; struct tpacket_rollover_stats rstats; + struct packet_rollover *rollover; if (level != SOL_PACKET) return -ENOPROTOOPT; @@ -3931,13 +3934,18 @@ static int packet_getsockopt(struct sock 0); break; case PACKET_ROLLOVER_STATS: - if (!po->rollover) + rcu_read_lock(); + rollover = rcu_dereference(po->rollover); + if (rollover) { + rstats.tp_all = atomic_long_read(&rollover->num); + rstats.tp_huge = atomic_long_read(&rollover->num_huge); + rstats.tp_failed = atomic_long_read(&rollover->num_failed); + data = &rstats; + lv = sizeof(rstats); + } + rcu_read_unlock(); + if (!rollover) return -EINVAL; - rstats.tp_all = atomic_long_read(&po->rollover->num); - rstats.tp_huge = atomic_long_read(&po->rollover->num_huge); - rstats.tp_failed = atomic_long_read(&po->rollover->num_failed); - data = &rstats; - lv = sizeof(rstats); break; case PACKET_TX_HAS_OFF: val = po->tp_tx_has_off;