[PATCH 09/18] p54: prevent bounds-check bypass via speculative execution

[Dan Williams <dan.j.williams@intel.com>]

Static analysis reports that 'queue' may be a user controlled value that
is used as a data dependency to read from the 'priv->qos_params' array.
In order to avoid potential leaks of kernel memory values, block
speculative execution of the instruction stream that could issue reads
based on an invalid result of 'priv->qos_params[queue]'.

Based on an original patch by Elena Reshetova.

Cc: Christian Lamparter <chunkeey@googlemail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/net/wireless/intersil/p54/main.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/intersil/p54/main.c b/drivers/net/wireless/intersil/p54/main.c
index ab6d39e12069..85c9cbee35fc 100644
--- a/drivers/net/wireless/intersil/p54/main.c
+++ b/drivers/net/wireless/intersil/p54/main.c
@@ -20,6 +20,7 @@
 #include <linux/firmware.h>
 #include <linux/etherdevice.h>
 #include <linux/module.h>
+#include <linux/compiler.h>
 
 #include <net/mac80211.h>
 
@@ -411,12 +412,13 @@ static int p54_conf_tx(struct ieee80211_hw *dev,
 		       const struct ieee80211_tx_queue_params *params)
 {
 	struct p54_common *priv = dev->priv;
+	struct p54_edcf_queue_param *p54_q;
 	int ret;
 
 	mutex_lock(&priv->conf_mutex);
-	if (queue < dev->queues) {
-		P54_SET_QUEUE(priv->qos_params[queue], params->aifs,
-			params->cw_min, params->cw_max, params->txop);
+	if ((p54_q = nospec_array_ptr(priv->qos_params, queue, dev->queues))) {
+		P54_SET_QUEUE(p54_q[0], params->aifs, params->cw_min,
+				params->cw_max, params->txop);
 		ret = p54_set_edcf(priv);
 	} else
 		ret = -EINVAL;