From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
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 ACCESS_ONCE() as suggested by Eric Dumazet and Josh
Triplett.
Reported-by: kbuild test robot <fengguang...@intel.com>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Alexey Kuznetsov <kuz...@ms2.inr.ac.ru>
Cc: James Morris <jmor...@namei.org>
Cc: Hideaki YOSHIFUJI <yoshf...@linux-ipv6.org>
Cc: Patrick McHardy <ka...@trash.net>
Cc: net...@vger.kernel.org
---
net/ipv6/ip6_gre.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 6b26e9feafb9..7bc9e1b3283e 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -276,7 +276,8 @@ 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);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(*tp) = t->next;
break;
}
}
--
1.8.1.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
