rtlwifi: Add the missing rcu_read_lock/unlock

===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
net/mac80211/sta_info.c:125 invoked rcu_dereference_check() without protection!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0
5 locks held by wpa_supplicant/468:
 #0:  (rtnl_mutex){+.+.+.}, at: [<c1465d84>] rtnl_lock+0x14/0x20
 #1:  (&rdev->mtx){+.+.+.}, at: [<f84b8c2b>] cfg80211_mgd_wext_siwfreq+0x6b/0x170 [cfg80211]
 #2:  (&rdev->devlist_mtx){+.+.+.}, at: [<f84b8c37>] cfg80211_mgd_wext_siwfreq+0x77/0x170 [cfg80211]
 #3:  (&wdev->mtx){+.+.+.}, at: [<f84b8c44>] cfg80211_mgd_wext_siwfreq+0x84/0x170 [cfg80211]
 #4:  (&rtlpriv->locks.conf_mutex){+.+.+.}, at: [<f8506476>] rtl_op_bss_info_changed+0x26/0xc10 [rtlwifi]

stack backtrace:
Pid: 468, comm: wpa_supplicant Not tainted 2.6.38-rc6+ #79
Call Trace:
 [<c108806a>] ? lockdep_rcu_dereference+0xaa/0xb0
 [<f8523d2c>] ? sta_info_get_bss+0x19c/0x1b0 [mac80211]
 [<f8523d62>] ? ieee80211_find_sta+0x22/0x40 [mac80211]
 [<f850661c>] ? rtl_op_bss_info_changed+0x1cc/0xc10 [rtlwifi]
 [<c153671c>] ? __mutex_unlock_slowpath+0x14c/0x160
 [<c153673d>] ? mutex_unlock+0xd/0x10
 [<f8507180>] ? rtl_op_config+0x120/0x310 [rtlwifi]
 [<c10896db>] ? trace_hardirqs_on+0xb/0x10
 [<f8522169>] ? ieee80211_bss_info_change_notify+0xf9/0x1f0 [mac80211]
 [<f8506450>] ? rtl_op_bss_info_changed+0x0/0xc10 [rtlwifi]
 [<f853646f>] ? ieee80211_set_channel+0xbf/0xd0 [mac80211]
 [<f84b5f41>] ? cfg80211_set_freq+0x121/0x180 [cfg80211]
 [<f85363b0>] ? ieee80211_set_channel+0x0/0xd0 [mac80211]
 [<f84b8ceb>] ? cfg80211_mgd_wext_siwfreq+0x12b/0x170 [cfg80211]
 [<f84b87eb>] ? cfg80211_wext_siwfreq+0x9b/0x100 [cfg80211]
 [<c153b98b>] ? sub_preempt_count+0x7b/0xb0
 [<c150f874>] ? ioctl_standard_call+0x74/0x3b0
 [<c1465d84>] ? rtnl_lock+0x14/0x20
 [<f84b8750>] ? cfg80211_wext_siwfreq+0x0/0x100 [cfg80211]
 [<c14568bd>] ? __dev_get_by_name+0x8d/0xb0
 [<c150fddb>] ? wext_handle_ioctl+0x16b/0x180
 [<f84b8750>] ? cfg80211_wext_siwfreq+0x0/0x100 [cfg80211]
 [<c145bc7a>] ? dev_ioctl+0x5ba/0x720
 [<c108a947>] ? __lock_acquire+0x3e7/0x19b0
 [<c1443b0b>] ? sock_ioctl+0x1eb/0x290
 [<c108bfa5>] ? lock_release_non_nested+0x95/0x2f0
 [<c1443920>] ? sock_ioctl+0x0/0x290
 [<c114d74d>] ? do_vfs_ioctl+0x7d/0x5c0
 [<c1112232>] ? might_fault+0x62/0xb0
 [<c113e3c6>] ? fget_light+0x226/0x390
 [<c1112278>] ? might_fault+0xa8/0xb0
 [<c114dd17>] ? sys_ioctl+0x87/0x90
 [<c1002f9f>] ? sysenter_do_call+0x12/0x38

This work was supported by a hardware donation from the CE Linux Forum.

Signed-off-by: Alessio Igor Bogani <abogani@kernel.org>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/net/wireless/rtlwifi/rtl8192cu/trx.c b/drivers/net/wireless/rtlwifi/rtl8192cu/trx.c
index 659e0ca95c64..d0b0d43b9a6d 100644
--- a/drivers/net/wireless/rtlwifi/rtl8192cu/trx.c
+++ b/drivers/net/wireless/rtlwifi/rtl8192cu/trx.c
@@ -504,7 +504,7 @@ void rtl92cu_tx_fill_desc(struct ieee80211_hw *hw,
 	struct rtl_mac *mac = rtl_mac(rtl_priv(hw));
 	struct rtl_ps_ctl *ppsc = rtl_psc(rtl_priv(hw));
 	bool defaultadapter = true;
-	struct ieee80211_sta *sta = ieee80211_find_sta(mac->vif, mac->bssid);
+	struct ieee80211_sta *sta;
 	struct rtl_tcb_desc tcb_desc;
 	u8 *qc = ieee80211_get_qos_ctl(hdr);
 	u8 tid = qc[0] & IEEE80211_QOS_CTL_TID_MASK;
@@ -562,10 +562,13 @@ void rtl92cu_tx_fill_desc(struct ieee80211_hw *hw,
 		SET_TX_DESC_DATA_BW(txdesc, 0);
 		SET_TX_DESC_DATA_SC(txdesc, 0);
 	}
+	rcu_read_lock();
+	sta = ieee80211_find_sta(mac->vif, mac->bssid);
 	if (sta) {
 		u8 ampdu_density = sta->ht_cap.ampdu_density;
 		SET_TX_DESC_AMPDU_DENSITY(txdesc, ampdu_density);
 	}
+	rcu_read_unlock();
 	if (info->control.hw_key) {
 		struct ieee80211_key_conf *keyconf = info->control.hw_key;
 		switch (keyconf->cipher) {