[PATCH v2 tip/core/rcu 08/13] ipv6/ip6_gre: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

The sparse checking for rcu_assign_pointer() was recently upgraded
to reject non-__kernel address spaces.  This also rejects __rcu,
which is almost always the right thing to do.  However, the use in
ip6gre_tunnel_unlink() is legitimate: It is assigning a pointer to an
element from an RCU-protected list, and all elements of this list are
already visible to caller.

This commit therefore silences this false positive by laundering the
pointer using rcu_access_pointer() as suggested by Josh Triplett.

Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>
Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>
Cc: Patrick McHardy <kaber@xxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
---
 net/ipv6/ip6_gre.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 6b26e9feafb9..a0b8f4056f05 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -276,7 +276,7 @@ static void ip6gre_tunnel_unlink(struct ip6gre_net *ign, struct ip6_tnl *t)
 	     (iter = rtnl_dereference(*tp)) != NULL;
 	     tp = &iter->next) {
 		if (t == iter) {
-			rcu_assign_pointer(*tp, t->next);
+			rcu_assign_pointer(*tp, rcu_access_pointer(t->next));
 			break;
 		}
 	}
-- 
1.8.1.5

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