Messages in this thread | | | Subject | Re: [PATCH v2 tip/core/rcu 07/13] ipv6/ip6_tunnel: Apply rcu_access_pointer() to avoid sparse false positive | From | Eric Dumazet <> | Date | Wed, 09 Oct 2013 14:42:29 -0700 |
| |
On Wed, 2013-10-09 at 14:29 -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" <paulmck@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 > ip6_tnl_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@intel.com> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru> > Cc: James Morris <jmorris@namei.org> > Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org> > Cc: Patrick McHardy <kaber@trash.net> > Cc: netdev@vger.kernel.org > --- > net/ipv6/ip6_tunnel.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c > index 61355f7f4da5..ecc0166e1a9c 100644 > --- a/net/ipv6/ip6_tunnel.c > +++ b/net/ipv6/ip6_tunnel.c > @@ -245,7 +245,7 @@ ip6_tnl_unlink(struct ip6_tnl_net *ip6n, 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; > } > }
Then it seems a mere "*tp = t->next;" would be enough ?
We do not really need a barrier.
| |