On Wed, Oct 09, 2013 at 03:28:42PM -0700, Josh Triplett wrote:
> On Wed, Oct 09, 2013 at 02:29:38PM -0700, Paul E. McKenney wrote:
> > 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
> > dn_insert_route() is legitimate: It is assigning a pointer to an element
>
> Nit: "uses ... are", not "use ... is". :)
Don't I already have "use ... is"?
Thanx, Paul
> > 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...@intel.com>
> > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> > Cc: "David S. Miller" <da...@davemloft.net>
> > Cc: Thomas Graf <tg...@suug.ch>
> > Cc: Gao feng <gaof...@cn.fujitsu.com>
> > Cc: Stephen Hemminger <shemmin...@vyatta.com>
> > Cc: linux-decnet-u...@lists.sourceforge.net
> > Cc: net...@vger.kernel.org
>
> With or without the above typo fix:
>
> Reviewed-by: Josh Triplett <j...@joshtriplett.org>
>
> > ---
> > net/decnet/dn_route.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
> > index fe32388ea24f..3b1357bcfc92 100644
> > --- a/net/decnet/dn_route.c
> > +++ b/net/decnet/dn_route.c
> > @@ -345,7 +345,7 @@ static int dn_insert_route(struct dn_route *rt,
> > unsigned int hash, struct dn_rou
> > /* Put it first */
> > *rthp = rth->dst.dn_next;
> > rcu_assign_pointer(rth->dst.dn_next,
> > - dn_rt_hash_table[hash].chain);
> > +
> > rcu_access_pointer(dn_rt_hash_table[hash].chain));
> > rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth);
> >
> > dst_use(&rth->dst, now);
> > @@ -358,7 +358,8 @@ static int dn_insert_route(struct dn_route *rt,
> > unsigned int hash, struct dn_rou
> > rthp = &rth->dst.dn_next;
> > }
> >
> > - rcu_assign_pointer(rt->dst.dn_next, dn_rt_hash_table[hash].chain);
> > + rcu_assign_pointer(rt->dst.dn_next,
> > + rcu_access_pointer(dn_rt_hash_table[hash].chain));
> > rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt);
> >
> > dst_use(&rt->dst, now);
> > --
> > 1.8.1.5
> >
>
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