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[PATCH v2 15/19] carl9170: prevent bounds-check bypass via speculative execution

Static analysis reports that 'queue' may be a user controlled value that
is used as a data dependency to read from the 'ar9170_qmap' 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 'ar9170_qmap[queue]'. In this case the
value of 'ar9170_qmap[queue]' is immediately reused as an index to the
'ar->edcf' array.

Based on an original patch by Elena Reshetova.

Cc: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>
Cc: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Cc: linux-wireless@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
 drivers/net/wireless/ath/carl9170/main.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/carl9170/main.c b/drivers/net/wireless/ath/carl9170/main.c
index 988c8857d78c..0acfa8c22b7d 100644
--- a/drivers/net/wireless/ath/carl9170/main.c
+++ b/drivers/net/wireless/ath/carl9170/main.c
@@ -41,6 +41,7 @@
 #include <linux/module.h>
 #include <linux/etherdevice.h>
 #include <linux/random.h>
+#include <linux/nospec.h>
 #include <net/mac80211.h>
 #include <net/cfg80211.h>
 #include "hw.h"
@@ -1384,11 +1385,13 @@ static int carl9170_op_conf_tx(struct ieee80211_hw *hw,
 			       const struct ieee80211_tx_queue_params *param)
 	struct ar9170 *ar = hw->priv;
+	const u8 *elem;
 	int ret;
-	if (queue < ar->hw->queues) {
-		memcpy(&ar->edcf[ar9170_qmap[queue]], param, sizeof(*param));
+	elem = array_ptr(ar9170_qmap, queue, ar->hw->queues);
+	if (elem) {
+		memcpy(&ar->edcf[*elem], param, sizeof(*param));
 		ret = carl9170_set_qos(ar);
 	} else {
 		ret = -EINVAL;