linux-kernel - [ 22/42] mac80211: fix non RCU-safe sta

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Date:	Thu, 14 Jun 2012 16:56:45 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Eyal Shapira <eyal@...ery.com>,
	Arik Nemtsov <arik@...ery.com>,
	"John W. Linville" <linville@...driver.com>
Subject: [ 22/42] mac80211: fix non RCU-safe sta_list manipulation

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arik Nemtsov <arik@...ery.com>

commit 794454ce72a298de6f4536ade597bdcc7dcde7c7 upstream.

sta_info_cleanup locks the sta_list using rcu_read_lock however
the delete operation isn't rcu safe. A race between sta_info_cleanup
timer being called and a STA being removed can occur which leads
to a panic while traversing sta_list. Fix this by switching to the
RCU-safe versions.

Reported-by: Eyal Shapira <eyal@...ery.com>
Signed-off-by: Arik Nemtsov <arik@...ery.com>
Signed-off-by: John W. Linville <linville@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/mac80211/sta_info.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -378,7 +378,7 @@ static int sta_info_insert_finish(struct
 	/* make the station visible */
 	sta_info_hash_add(local, sta);
 
-	list_add(&sta->list, &local->sta_list);
+	list_add_rcu(&sta->list, &local->sta_list);
 
 	set_sta_flag(sta, WLAN_STA_INSERTED);
 
@@ -688,7 +688,7 @@ int __must_check __sta_info_destroy(stru
 	if (ret)
 		return ret;
 
-	list_del(&sta->list);
+	list_del_rcu(&sta->list);
 
 	mutex_lock(&local->key_mtx);
 	for (i = 0; i < NUM_DEFAULT_KEYS; i++)


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