Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756151AbdGCOoS (ORCPT ); Mon, 3 Jul 2017 10:44:18 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:35584 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932359AbdGCNlN (ORCPT ); Mon, 3 Jul 2017 09:41:13 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wei Wang , Martin KaFai Lau , "David S. Miller" Subject: [PATCH 4.9 021/172] decnet: always not take dst->__refcnt when inserting dst into hash table Date: Mon, 3 Jul 2017 15:33:21 +0200 Message-Id: <20170703133415.239363144@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133414.260777365@linuxfoundation.org> References: <20170703133414.260777365@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2977 Lines: 89 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wei Wang [ Upstream commit 76371d2e3ad1f84426a30ebcd8c3b9b98f4c724f ] In the existing dn_route.c code, dn_route_output_slow() takes dst->__refcnt before calling dn_insert_route() while dn_route_input_slow() does not take dst->__refcnt before calling dn_insert_route(). This makes the whole routing code very buggy. In dn_dst_check_expire(), dnrt_free() is called when rt expires. This makes the routes inserted by dn_route_output_slow() not able to be freed as the refcnt is not released. In dn_dst_gc(), dnrt_drop() is called to release rt which could potentially cause the dst->__refcnt to be dropped to -1. In dn_run_flush(), dst_free() is called to release all the dst. Again, it makes the dst inserted by dn_route_output_slow() not able to be released and also, it does not wait on the rcu and could potentially cause crash in the path where other users still refer to this dst. This patch makes sure both input and output path do not take dst->__refcnt before calling dn_insert_route() and also makes sure dnrt_free()/dst_free() is called when removing dst from the hash table. The only difference between those 2 calls is that dnrt_free() waits on the rcu while dst_free() does not. Signed-off-by: Wei Wang Acked-by: Martin KaFai Lau Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/decnet/dn_route.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) --- a/net/decnet/dn_route.c +++ b/net/decnet/dn_route.c @@ -188,12 +188,6 @@ static inline void dnrt_free(struct dn_r call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free); } -static inline void dnrt_drop(struct dn_route *rt) -{ - dst_release(&rt->dst); - call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free); -} - static void dn_dst_check_expire(unsigned long dummy) { int i; @@ -248,7 +242,7 @@ static int dn_dst_gc(struct dst_ops *ops } *rtp = rt->dst.dn_next; rt->dst.dn_next = NULL; - dnrt_drop(rt); + dnrt_free(rt); break; } spin_unlock_bh(&dn_rt_hash_table[i].lock); @@ -350,7 +344,7 @@ static int dn_insert_route(struct dn_rou dst_use(&rth->dst, now); spin_unlock_bh(&dn_rt_hash_table[hash].lock); - dnrt_drop(rt); + dst_free(&rt->dst); *rp = rth; return 0; } @@ -380,7 +374,7 @@ static void dn_run_flush(unsigned long d for(; rt; rt = next) { next = rcu_dereference_raw(rt->dst.dn_next); RCU_INIT_POINTER(rt->dst.dn_next, NULL); - dst_free((struct dst_entry *)rt); + dnrt_free(rt); } nothing_to_declare: @@ -1187,7 +1181,7 @@ make_route: if (dev_out->flags & IFF_LOOPBACK) flags |= RTCF_LOCAL; - rt = dst_alloc(&dn_dst_ops, dev_out, 1, DST_OBSOLETE_NONE, DST_HOST); + rt = dst_alloc(&dn_dst_ops, dev_out, 0, DST_OBSOLETE_NONE, DST_HOST); if (rt == NULL) goto e_nobufs;