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 uses in
sta_info_hash_del() are legitimate: They are 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: "John W. Linville" <linvi...@tuxdriver.com>
Cc: Johannes Berg <johan...@sipsolutions.net>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: linux-wirel...@vger.kernel.org
Cc: net...@vger.kernel.org
---
net/mac80211/sta_info.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index aeb967a0aeed..494f03c0831f 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -74,8 +74,8 @@ static int sta_info_hash_del(struct ieee80211_local *local,
if (!s)
return -ENOENT;
if (s == sta) {
- rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)],
- s->hnext);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(local->sta_hash[STA_HASH(sta->sta.addr)]) =
s->hnext;
return 0;
}
@@ -84,7 +84,8 @@ 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);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(s->hnext) = sta->hnext;
return 0;
}
--
1.8.1.5
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