[PATCH tip/core/rcu 0/13] Sparse-related updates for 3.13

[PATCH tip/core/rcu 0/13] Sparse-related updates for 3.13

[Paul E. McKenney]

Hello!

This series features updates to allow sparse to do a better job of
statically analyzing RCU usage:

1.	Apply ACCESS_ONCE() to rcu_assign_pointer()'s target to prevent
	comiler mischief.  Also require that the source pointer be from
	the kernel address space.  Sometimes it can be from the RCU address
	space, which necessitates the remaining patches in this series.
	Which, it must be admitted, apply to a very small fraction of
	the rcu_assign_pointer() invocations in the kernel.  This commit
	courtesy of Josh Triplett.

2-13.	Apply rcu_access_pointer() to avoid a number of false positives.

							Thanx, Paul


 b/drivers/net/bonding/bond_alb.c  |    3 ++-
 b/drivers/net/bonding/bond_main.c |    8 +++++---
 b/include/linux/rcupdate.h        |   12 +++++++++++-
 b/kernel/notifier.c               |    2 +-
 b/net/bridge/br_mdb.c             |    2 +-
 b/net/bridge/br_multicast.c       |    4 ++--
 b/net/decnet/dn_route.c           |    5 +++--
 b/net/ipv4/ip_sockglue.c          |    2 +-
 b/net/ipv6/ip6_gre.c              |    2 +-
 b/net/ipv6/ip6_tunnel.c           |    2 +-
 b/net/ipv6/sit.c                  |    2 +-
 b/net/mac80211/sta_info.c         |    4 ++--
 b/net/wireless/scan.c             |   14 +++++++-------
 13 files changed, 38 insertions(+), 24 deletions(-)

[PATCH tip/core/rcu 01/13] rcu: Make rcu_assign_pointer's assignment volatile and type-safe

[Paul E. McKenney]

From: Josh Triplett <josh@joshtriplett.org>

rcu_assign_pointer needs to use ACCESS_ONCE to make the assignment to
the destination pointer volatile, to protect against compilers too
clever for their own good.

In addition, since rcu_assign_pointer force-casts the source pointer to
add the __rcu address space (overriding any existing address space), add
an explicit check that the source pointer has the __kernel address space
to start with.

This new check produces warnings like this, when attempting to assign
from a __user pointer:

test.c:25:9: warning: incorrect type in argument 2 (different address spaces)
test.c:25:9:    expected struct foo *<noident>
test.c:25:9:    got struct foo [noderef] <asn:1>*badsrc

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/rcupdate.h | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f1f1bc3..5b444e0 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -506,8 +506,17 @@ static inline void rcu_preempt_sleep_check(void)
 #ifdef __CHECKER__
 #define rcu_dereference_sparse(p, space) \
 	((void)(((typeof(*p) space *)p) == p))
+/* The dummy first argument in __rcu_assign_pointer_typecheck makes the
+ * typechecked pointer the second argument, matching rcu_assign_pointer itself;
+ * this avoids confusion about argument numbers in warning messages. */
+#define __rcu_assign_pointer_check_kernel(v) \
+	do { \
+		extern void __rcu_assign_pointer_typecheck(int, typeof(*(v)) __kernel *); \
+		__rcu_assign_pointer_typecheck(0, v); \
+	} while (0)
 #else /* #ifdef __CHECKER__ */
 #define rcu_dereference_sparse(p, space)
+#define __rcu_assign_pointer_check_kernel(v) do { } while (0)
 #endif /* #else #ifdef __CHECKER__ */
 
 #define __rcu_access_pointer(p, space) \
@@ -551,7 +560,8 @@ static inline void rcu_preempt_sleep_check(void)
 #define __rcu_assign_pointer(p, v, space) \
 	do { \
 		smp_wmb(); \
-		(p) = (typeof(*v) __force space *)(v); \
+		__rcu_assign_pointer_check_kernel(v); \
+		ACCESS_ONCE(p) = (typeof(*(v)) __force space *)(v); \
 	} while (0)
 
 
-- 
1.8.1.5

[PATCH tip/core/rcu 02/13] notifiers: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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
notifier_chain_unregister() is legitimate: It is deleting 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>
---
 kernel/notifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/notifier.c b/kernel/notifier.c
index 2d5cc4c..1857c71 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -51,7 +51,7 @@ static int notifier_chain_unregister(struct notifier_block **nl,
 {
 	while ((*nl) != NULL) {
 		if ((*nl) == n) {
-			rcu_assign_pointer(*nl, n->next);
+			rcu_assign_pointer(*nl, rcu_access_pointer(n->next));
 			return 0;
 		}
 		nl = &((*nl)->next);
-- 
1.8.1.5

[PATCH tip/core/rcu 03/13] bridge: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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 uses in
br_multicast_del_pg() and br_multicast_new_port_group() are legitimate:
They 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 these false positives by laundering the
pointers 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: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: bridge@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
---
 net/bridge/br_multicast.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index d1c5786..314c81c 100644
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -267,7 +267,7 @@ static void br_multicast_del_pg(struct net_bridge *br,
 		if (p != pg)
 			continue;
 
-		rcu_assign_pointer(*pp, p->next);
+		rcu_assign_pointer(*pp, rcu_access_pointer(p->next));
 		hlist_del_init(&p->mglist);
 		del_timer(&p->timer);
 		call_rcu_bh(&p->rcu, br_multicast_free_pg);
@@ -646,7 +646,7 @@ struct net_bridge_port_group *br_multicast_new_port_group(
 	p->addr = *group;
 	p->port = port;
 	p->state = state;
-	rcu_assign_pointer(p->next, next);
+	rcu_assign_pointer(p->next, rcu_access_pointer(next));
 	hlist_add_head(&p->mglist, &port->mglist);
 	setup_timer(&p->timer, br_multicast_port_group_expired,
 		    (unsigned long)p);
-- 
1.8.1.5

[PATCH tip/core/rcu 04/13] wireless: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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 uses in
cfg80211_combine_bsses() and cfg80211_bss_update() are legitimate:
They 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 these false positives by laundering the
pointers 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: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: bridge@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
---
 net/wireless/scan.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index eeb7148..edde117 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -671,7 +671,7 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *dev,
 		bss->pub.hidden_beacon_bss = &new->pub;
 		new->refcount += bss->refcount;
 		rcu_assign_pointer(bss->pub.beacon_ies,
-				   new->pub.beacon_ies);
+				   rcu_access_pointer(new->pub.beacon_ies));
 	}
 
 	return true;
@@ -706,10 +706,10 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 			old = rcu_access_pointer(found->pub.proberesp_ies);
 
 			rcu_assign_pointer(found->pub.proberesp_ies,
-					   tmp->pub.proberesp_ies);
+					   rcu_access_pointer(tmp->pub.proberesp_ies));
 			/* Override possible earlier Beacon frame IEs */
 			rcu_assign_pointer(found->pub.ies,
-					   tmp->pub.proberesp_ies);
+					   rcu_access_pointer(tmp->pub.proberesp_ies));
 			if (old)
 				kfree_rcu((struct cfg80211_bss_ies *)old,
 					  rcu_head);
@@ -740,12 +740,12 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 			old = rcu_access_pointer(found->pub.beacon_ies);
 
 			rcu_assign_pointer(found->pub.beacon_ies,
-					   tmp->pub.beacon_ies);
+					   rcu_access_pointer(tmp->pub.beacon_ies));
 
 			/* Override IEs if they were from a beacon before */
 			if (old == rcu_access_pointer(found->pub.ies))
 				rcu_assign_pointer(found->pub.ies,
-						   tmp->pub.beacon_ies);
+						   rcu_access_pointer(tmp->pub.beacon_ies));
 
 			/* Assign beacon IEs to all sub entries */
 			list_for_each_entry(bss, &found->hidden_list,
@@ -756,7 +756,7 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 				WARN_ON(ies != old);
 
 				rcu_assign_pointer(bss->pub.beacon_ies,
-						   tmp->pub.beacon_ies);
+						   rcu_access_pointer(tmp->pub.beacon_ies));
 			}
 
 			if (old)
@@ -804,7 +804,7 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 					 &hidden->hidden_list);
 				hidden->refcount++;
 				rcu_assign_pointer(new->pub.beacon_ies,
-						   hidden->pub.beacon_ies);
+						   rcu_access_pointer(hidden->pub.beacon_ies));
 			}
 		} else {
 			/*
-- 
1.8.1.5

Re: [PATCH tip/core/rcu 04/13] wireless: Apply rcu_access_pointer() to avoid sparse false positive

[Ben Hutchings]

On Tue, 2013-09-24 at 18:35 -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 uses in
> cfg80211_combine_bsses() and cfg80211_bss_update() are legitimate:
> They is assigning a pointer to an element from an RCU-protected list,
[...]

'They is'?  This error is also in the commit messsages for the bridge
and mac80211 patches, and maybe others that weren't sent to netdev.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH tip/core/rcu 04/13] wireless: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

On Wed, Sep 25, 2013 at 06:48:23PM +0100, Ben Hutchings wrote:
> On Tue, 2013-09-24 at 18:35 -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 uses in
> > cfg80211_combine_bsses() and cfg80211_bss_update() are legitimate:
> > They is assigning a pointer to an element from an RCU-protected list,
> [...]
> 
> 'They is'?  This error is also in the commit messsages for the bridge
> and mac80211 patches, and maybe others that weren't sent to netdev.

Good catch, fixed in four patches.  Yeah, English can be a bit
unfriendly at times to text reuse.  The s/It/They/ should have been
s/It is/They are/.  ;-)

							Thanx, Paul

[PATCH tip/core/rcu 05/13] decnet: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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
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
---
 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 fe32388..3b1357b 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

[PATCH tip/core/rcu 06/13] ipv4/ip_socketglue: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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
ip_ra_control() 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/ipv4/ip_sockglue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index d9c4f11..d328f15 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -269,7 +269,7 @@ int ip_ra_control(struct sock *sk, unsigned char on,
 			}
 			/* dont let ip_call_ra_chain() use sk again */
 			ra->sk = NULL;
-			rcu_assign_pointer(*rap, ra->next);
+			rcu_assign_pointer(*rap, rcu_access_pointer(ra->next));
 			spin_unlock_bh(&ip_ra_lock);
 
 			if (ra->destructor)
-- 
1.8.1.5

[PATCH tip/core/rcu 07/13] ipv6/ip6_tunnel: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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 61355f7..ecc0166e 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;
 		}
 	}
-- 
1.8.1.5

[PATCH 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@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 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_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 6b26e9f..a0b8f40 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

[PATCH tip/core/rcu 09/13] ipv6/sit: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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
ipip6_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@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/sit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 7ee5cb9..fcb050a 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -157,7 +157,7 @@ static void ipip6_tunnel_unlink(struct sit_net *sitn, struct ip_tunnel *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

[PATCH tip/core/rcu 10/13] mac80211: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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 uses in
sta_info_hash_del() are legitimate: They 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: "John W. Linville" <linville@tuxdriver.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
---
 net/mac80211/sta_info.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index aeb967a..d18ab89 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -75,7 +75,7 @@ static int sta_info_hash_del(struct ieee80211_local *local,
 		return -ENOENT;
 	if (s == sta) {
 		rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)],
-				   s->hnext);
+				   rcu_access_pointer(s->hnext));
 		return 0;
 	}
 
@@ -84,7 +84,7 @@ static int sta_info_hash_del(struct ieee80211_local *local,
 		s = rcu_dereference_protected(s->hnext,
 					lockdep_is_held(&local->sta_mtx));
 	if (rcu_access_pointer(s->hnext)) {
-		rcu_assign_pointer(s->hnext, sta->hnext);
+		rcu_assign_pointer(s->hnext, rcu_access_pointer(sta->hnext));
 		return 0;
 	}
 
-- 
1.8.1.5

[PATCH tip/core/rcu 11/13] bridge/br_mdb: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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
__br_mdb_del() is legitimate: They 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 these false positives by laundering the
pointers 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: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: bridge@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
---
 net/bridge/br_mdb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index 85a09bb..3184c88 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -447,7 +447,7 @@ static int __br_mdb_del(struct net_bridge *br, struct br_mdb_entry *entry)
 		if (p->port->state == BR_STATE_DISABLED)
 			goto unlock;
 
-		rcu_assign_pointer(*pp, p->next);
+		rcu_assign_pointer(*pp, rcu_access_pointer(p->next));
 		hlist_del_init(&p->mglist);
 		del_timer(&p->timer);
 		call_rcu_bh(&p->rcu, br_multicast_free_pg);
-- 
1.8.1.5

[PATCH tip/core/rcu 12/13] bonding/bond_main: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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 uses in
bond_change_active_slave(), bond_enslave(), and __bond_release_one()
are legitimate: They are assigning a pointer to an element from an
RCU-protected list (or a NULL pointer), and all elements of this list
are already visible to caller.

This commit therefore silences these false positives either by laundering
the pointers using rcu_access_pointer() as suggested by Josh Triplett,
or by using RCU_INIT_POINTER() for NULL pointer assignments.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: bridge@lists.linux-foundation.org
Cc: netdev@vger.kernel.org
---
 drivers/net/bonding/bond_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 72df399..2f276b9 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -890,7 +890,8 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active)
 		if (new_active)
 			bond_set_slave_active_flags(new_active);
 	} else {
-		rcu_assign_pointer(bond->curr_active_slave, new_active);
+		rcu_assign_pointer(bond->curr_active_slave,
+				   rcu_access_pointer(new_active));
 	}
 
 	if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) {
@@ -1601,7 +1602,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 		 * so we can change it without calling change_active_interface()
 		 */
 		if (!bond->curr_active_slave && new_slave->link == BOND_LINK_UP)
-			rcu_assign_pointer(bond->curr_active_slave, new_slave);
+			rcu_assign_pointer(bond->curr_active_slave,
+					   rcu_access_pointer(new_slave));
 
 		break;
 	} /* switch(bond_mode) */
@@ -1801,7 +1803,7 @@ static int __bond_release_one(struct net_device *bond_dev,
 	}
 
 	if (all) {
-		rcu_assign_pointer(bond->curr_active_slave, NULL);
+		RCU_INIT_POINTER(bond->curr_active_slave, NULL);
 	} else if (oldcurrent == slave) {
 		/*
 		 * Note that we hold RTNL over this sequence, so there
-- 
1.8.1.5

[PATCH tip/core/rcu 13/13] bonding/bond_alb.c: Apply rcu_access_pointer() to avoid sparse false positive

[Paul E. McKenney]

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
bond_alb_handle_active_change() 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
---
 drivers/net/bonding/bond_alb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 91f179d..cdd697c 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -1667,7 +1667,8 @@ void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave
 	}
 
 	swap_slave = bond->curr_active_slave;
-	rcu_assign_pointer(bond->curr_active_slave, new_slave);
+	rcu_assign_pointer(bond->curr_active_slave,
+			   rcu_access_pointer(new_slave));
 
 	if (!new_slave || list_empty(&bond->slave_list))
 		return;
-- 
1.8.1.5