[PATCH 08/18] carl9170: prevent bounds-check bypass via speculative execution

[Dan Williams]

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 <chunk...@googlemail.com>
Cc: Kalle Valo <kv...@codeaurora.org>
Cc: linux-wirel...@vger.kernel.org
Cc: net...@vger.kernel.org
Signed-off-by: Elena Reshetova <elena.reshet...@intel.com>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/net/wireless/ath/carl9170/main.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/carl9170/main.c 
b/drivers/net/wireless/ath/carl9170/main.c
index 988c8857d78c..0ff34cbe2b62 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/compiler.h>
 #include <net/mac80211.h>
 #include <net/cfg80211.h>
 #include "hw.h"
@@ -1384,11 +1385,12 @@ 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;
 
        mutex_lock(&ar->mutex);
-       if (queue < ar->hw->queues) {
-               memcpy(&ar->edcf[ar9170_qmap[queue]], param, sizeof(*param));
+       if ((elem = nospec_array_ptr(ar9170_qmap, queue, ar->hw->queues))) {
+               memcpy(&ar->edcf[*elem], param, sizeof(*param));
                ret = carl9170_set_qos(ar);
        } else {
                ret = -EINVAL;