From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/13] wireless: Apply rcu_access_pointer() to avoid sparse false positive Date: Tue, 24 Sep 2013 18:35:07 -0700 Message-ID: <1380072916-31557-4-git-send-email-paulmck@linux.vnet.ibm.com> References: <20130925013451.GA31260@linux.vnet.ibm.com> <1380072916-31557-1-git-send-email-paulmck@linux.vnet.ibm.com> Cc: Stephen Hemminger , tglx@linutronix.de, laijs@cn.fujitsu.com, edumazet@google.com, peterz@infradead.org, fweisbec@gmail.com, bridge@lists.linux-foundation.org, josh@joshtriplett.org, rostedt@goodmis.org, "David S. Miller" , dhowells@redhat.com, sbw@mit.edu, niv@us.ibm.com, netdev@vger.kernel.org, mathieu.desnoyers@efficios.com, dipankar@in.ibm.com, darren@dvhart.com, akpm@linux-foundation.org, "Paul E. McKenney" , mingo@kernel.org To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1380072916-31557-1-git-send-email-paulmck@linux.vnet.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: bridge-bounces@lists.linux-foundation.org Errors-To: bridge-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org From: "Paul E. McKenney" 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 Signed-off-by: Paul E. McKenney Cc: Stephen Hemminger Cc: "David S. Miller" 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