linux-kernel - [PATCH 3.16 010/305] ipv6: Fix another sparse warning on rt6i

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Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>
Subject: [PATCH 3.16 010/305] ipv6: Fix another sparse warning on rt6i_node

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@...adent.org.uk>

Commit 0933273ce750 "ipv6: fix sparse warning on rt6i_node" fixed some
sparse warnings in ip6_fib.c, but introduced a new one in
fib6_update_sernum() (which was removed before the corresponding
upstream commit).

fib6_update_sernum() is called in a RCU read-side section, so use
rcu_dereference() to read rt6_info::rt6i_node.

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1681,10 +1681,10 @@ static void fib6_prune_clones(struct net
 static int fib6_update_sernum(struct rt6_info *rt, void *arg)
 {
 	__u32 sernum = *(__u32 *)arg;
+	struct fib6_node *fn = rcu_dereference(rt->rt6i_node);

-	if (rt->rt6i_node &&
-	    rt->rt6i_node->fn_sernum != sernum)
-		rt->rt6i_node->fn_sernum = sernum;
+	if (fn && fn->fn_sernum != sernum)
+		fn->fn_sernum = sernum;

 	return 0;
 }