[PATCH 4.19 18/79] nl80211: Fix possible Spectre-v1 for CQM RSSI thresholds

Greg Kroah-Hartman
2019-09-19T22:32:59Z

From: Masashi Honma <masashi.honma@gmail.com>

commit 4b2c5a14cd8005a900075f7dfec87473c6ee66fb upstream.

commit 1222a1601488 ("nl80211: Fix possible Spectre-v1 for CQM
RSSI thresholds") was incomplete and requires one more fix to
prevent accessing to rssi_thresholds[n] because user can control
rssi_thresholds[i] values to make i reach to n. For example,
rssi_thresholds = {-400, -300, -200, -100} when last is -34.

Cc: stable@vger.kernel.org
Fixes: 1222a1601488 ("nl80211: Fix possible Spectre-v1 for CQM RSSI thresholds")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
Link: https://lore.kernel.org/r/20190908005653.17433-1-masashi.honma@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/wireless/nl80211.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -10270,9 +10270,11 @@ static int cfg80211_cqm_rssi_update(stru
hyst = wdev->cqm_config->rssi_hyst;
n = wdev->cqm_config->n_rssi_thresholds;

- for (i = 0; i < n; i++)
+ for (i = 0; i < n; i++) {
+ i = array_index_nospec(i, n);
if (last < wdev->cqm_config->rssi_thresholds[i])
break;
+ }

low_index = i - 1;
if (low_index >= 0) {