lkml.org 
[lkml]   [2013]   [Oct]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 tip/core/rcu 05/13] decnet: Apply rcu_access_pointer() to avoid sparse false positive
On Wed, Oct 09, 2013 at 02:29:38PM -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
> dn_insert_route() is legitimate: It is assigning a pointer to an element

Nit: "uses ... are", not "use ... is". :)

> 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: Thomas Graf <tgraf@suug.ch>
> Cc: Gao feng <gaofeng@cn.fujitsu.com>
> Cc: Stephen Hemminger <shemminger@vyatta.com>
> Cc: linux-decnet-user@lists.sourceforge.net
> Cc: netdev@vger.kernel.org

With or without the above typo fix:

Reviewed-by: Josh Triplett <josh@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
>


\
 
 \ /
  Last update: 2013-10-10 00:41    [W:0.162 / U:0.364 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site