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
cfg80211_combine_bsses() and cfg80211_bss_update() 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 these false positives by laundering
the pointers 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: Stephen Hemminger <step...@networkplumber.org>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: bri...@lists.linux-foundation.org
Cc: net...@vger.kernel.org
---
net/wireless/scan.c | 32 ++++++++++++++++++--------------
1 file changed, 18 insertions(+), 14 deletions(-)
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index eeb71480f1af..ac3a47abf195 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -670,8 +670,8 @@ static bool cfg80211_combine_bsses(struct
cfg80211_registered_device *dev,
list_add(&bss->hidden_list, &new->hidden_list);
bss->pub.hidden_beacon_bss = &new->pub;
new->refcount += bss->refcount;
- rcu_assign_pointer(bss->pub.beacon_ies,
- new->pub.beacon_ies);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(bss->pub.beacon_ies) = new->pub.beacon_ies;
}
return true;
@@ -705,11 +705,12 @@ 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);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(found->pub.proberesp_ies) =
+ tmp->pub.proberesp_ies;
/* Override possible earlier Beacon frame IEs */
- rcu_assign_pointer(found->pub.ies,
- tmp->pub.proberesp_ies);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(found->pub.ies) = tmp->pub.proberesp_ies;
if (old)
kfree_rcu((struct cfg80211_bss_ies *)old,
rcu_head);
@@ -739,13 +740,14 @@ 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);
+ /* Both --rcu and visible, so ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(found->pub.beacon_ies) =
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);
+ /* Both --rcu & visible, ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(found->pub.ies) =
+ tmp->pub.beacon_ies;
/* Assign beacon IEs to all sub entries */
list_for_each_entry(bss, &found->hidden_list,
@@ -755,8 +757,9 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
ies = rcu_access_pointer(bss->pub.beacon_ies);
WARN_ON(ies != old);
- rcu_assign_pointer(bss->pub.beacon_ies,
- tmp->pub.beacon_ies);
+ /* Both --rcu & visible, ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(bss->pub.beacon_ies) =
+ tmp->pub.beacon_ies;
}
if (old)
@@ -803,8 +806,9 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
list_add(&new->hidden_list,
&hidden->hidden_list);
hidden->refcount++;
- rcu_assign_pointer(new->pub.beacon_ies,
- hidden->pub.beacon_ies);
+ /* Both --rcu & visible, ACCESS_ONCE() is OK. */
+ ACCESS_ONCE(new->pub.beacon_ies) =
+ hidden->pub.beacon_ies;
}
} else {
/*
--
1.8.1.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
