[PATCH] net: wireless: iwlegacy: Fix possible data races in il4965_send_rxon_assoc()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

CPU0:
il4965_configure_filter
	mutex_lock()
	line 6183: il->staging.filter_flags &= ... [WRITE]
	line 6184: il->staging.filter_flags |= ... [WRITE]

CPU1:
il4965_send_rxon_assoc
	line 1301: rxon1->filter_flags, rxon1->filter_flags [READ]
	line 1314: il->staging.filter_flags [READ]

The WRITE operations in CPU0 are performed with holding a mutex lock, 
but the READ operations in CPU1 are performed without holding this lock, 
so there may exist data races. 

These possible races are detected by a runtime testing. 
To fix these races, the mutex lock is used in il4965_send_rxon_assoc() 
to protect the data.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/net/wireless/intel/iwlegacy/4965.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/wireless/intel/iwlegacy/4965.c b/drivers/net/wireless/intel/iwlegacy/4965.c
index c3c638ed0ed7..45342777a5f1 100644
--- a/drivers/net/wireless/intel/iwlegacy/4965.c
+++ b/drivers/net/wireless/intel/iwlegacy/4965.c
@@ -1297,6 +1297,7 @@ il4965_send_rxon_assoc(struct il_priv *il)
 	const struct il_rxon_cmd *rxon1 = &il->staging;
 	const struct il_rxon_cmd *rxon2 = &il->active;
 
+	mutex_lock(&il->mutex);
 	if (rxon1->flags == rxon2->flags &&
 	    rxon1->filter_flags == rxon2->filter_flags &&
 	    rxon1->cck_basic_rates == rxon2->cck_basic_rates &&
@@ -1307,6 +1308,7 @@ il4965_send_rxon_assoc(struct il_priv *il)
 	    rxon1->rx_chain == rxon2->rx_chain &&
 	    rxon1->ofdm_basic_rates == rxon2->ofdm_basic_rates) {
 		D_INFO("Using current RXON_ASSOC.  Not resending.\n");
+		mutex_unlock(&il->mutex);
 		return 0;
 	}
 
@@ -1321,6 +1323,8 @@ il4965_send_rxon_assoc(struct il_priv *il)
 	    il->staging.ofdm_ht_dual_stream_basic_rates;
 	rxon_assoc.rx_chain_select_flags = il->staging.rx_chain;
 
+	mutex_unlock(&il->mutex);
+
 	ret =
 	    il_send_cmd_pdu_async(il, C_RXON_ASSOC, sizeof(rxon_assoc),
 				  &rxon_assoc, NULL);
-- 
2.17.0