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

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Hello!

On 1/6/2018 4:10 AM, Dan Williams wrote:

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 |    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))) {

I bet this causes checkpatch.pl to complain. I don't see a dire need to upset it here, the assignment may well precede *if*...

+		memcpy(&ar->edcf[*elem], param, sizeof(*param));
  		ret = carl9170_set_qos(ar);
  	} else {
  		ret = -EINVAL;


MBR, Sergei



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