releases/5.10.84/ipv4-convert-fib_num_tclassid_users-to-atomic_t.patch

From 213f5f8f31f10aa1e83187ae20fb7fa4e626b724 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 1 Dec 2021 18:26:35 -0800
Subject: ipv4: convert fib_num_tclassid_users to atomic_t

From: Eric Dumazet <edumazet@google.com>

commit 213f5f8f31f10aa1e83187ae20fb7fa4e626b724 upstream.

Before commit faa041a40b9f ("ipv4: Create cleanup helper for fib_nh")
changes to net->ipv4.fib_num_tclassid_users were protected by RTNL.

After the change, this is no longer the case, as free_fib_info_rcu()
runs after rcu grace period, without rtnl being held.

Fixes: faa041a40b9f ("ipv4: Create cleanup helper for fib_nh")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Ahern <dsahern@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/ip_fib.h     |    2 +-
 include/net/netns/ipv4.h |    2 +-
 net/ipv4/fib_frontend.c  |    2 +-
 net/ipv4/fib_rules.c     |    4 ++--
 net/ipv4/fib_semantics.c |    4 ++--
 5 files changed, 7 insertions(+), 7 deletions(-)

--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -437,7 +437,7 @@ int fib_validate_source(struct sk_buff *
 #ifdef CONFIG_IP_ROUTE_CLASSID
 static inline int fib_num_tclassid_users(struct net *net)
 {
-	return net->ipv4.fib_num_tclassid_users;
+	return atomic_read(&net->ipv4.fib_num_tclassid_users);
 }
 #else
 static inline int fib_num_tclassid_users(struct net *net)
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -61,7 +61,7 @@ struct netns_ipv4 {
 #endif
 	bool			fib_has_custom_local_routes;
 #ifdef CONFIG_IP_ROUTE_CLASSID
-	int			fib_num_tclassid_users;
+	atomic_t		fib_num_tclassid_users;
 #endif
 	struct hlist_head	*fib_table_hash;
 	bool			fib_offload_disabled;
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1578,7 +1578,7 @@ static int __net_init fib_net_init(struc
 	int error;
 
 #ifdef CONFIG_IP_ROUTE_CLASSID
-	net->ipv4.fib_num_tclassid_users = 0;
+	atomic_set(&net->ipv4.fib_num_tclassid_users, 0);
 #endif
 	error = ip_fib_net_init(net);
 	if (error < 0)
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -264,7 +264,7 @@ static int fib4_rule_configure(struct fi
 	if (tb[FRA_FLOW]) {
 		rule4->tclassid = nla_get_u32(tb[FRA_FLOW]);
 		if (rule4->tclassid)
-			net->ipv4.fib_num_tclassid_users++;
+			atomic_inc(&net->ipv4.fib_num_tclassid_users);
 	}
 #endif
 
@@ -296,7 +296,7 @@ static int fib4_rule_delete(struct fib_r
 
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	if (((struct fib4_rule *)rule)->tclassid)
-		net->ipv4.fib_num_tclassid_users--;
+		atomic_dec(&net->ipv4.fib_num_tclassid_users);
 #endif
 	net->ipv4.fib_has_custom_rules = true;
 
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -222,7 +222,7 @@ void fib_nh_release(struct net *net, str
 {
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	if (fib_nh->nh_tclassid)
-		net->ipv4.fib_num_tclassid_users--;
+		atomic_dec(&net->ipv4.fib_num_tclassid_users);
 #endif
 	fib_nh_common_release(&fib_nh->nh_common);
 }
@@ -633,7 +633,7 @@ int fib_nh_init(struct net *net, struct
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	nh->nh_tclassid = cfg->fc_flow;
 	if (nh->nh_tclassid)
-		net->ipv4.fib_num_tclassid_users++;
+		atomic_inc(&net->ipv4.fib_num_tclassid_users);
 #endif
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 	nh->fib_nh_weight = nh_weight;