[PATCH AUTOSEL 4.14 33/61] nl80211: Fix possible Spectre-v1 for CQM RSSI thresholds

Sasha Levin
2018-10-16T04:14:38Z

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

[ Upstream commit 1222a16014888ed9733c11e221730d4a8196222b ]

Use array_index_nospec() to sanitize i with respect to speculation.

Note that the user doesn't control i directly, but can make it out
of bounds by not finding a threshold in the array.

Signed-off-by: Masashi Honma <masashi.honma@gmail.com>
[add note about user control, as explained by Masashi]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/wireless/nl80211.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 5e7c9b361e8a..46e9812d13c0 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -9720,7 +9720,7 @@ static int cfg80211_cqm_rssi_update(struct cfg80211_registered_device *rdev,
struct wireless_dev *wdev = dev->ieee80211_ptr;
s32 last, low, high;
u32 hyst;
- int i, n;
+ int i, n, low_index;
int err;

/* RSSI reporting disabled? */
@@ -9757,10 +9757,19 @@ static int cfg80211_cqm_rssi_update(struct cfg80211_registered_device *rdev,
if (last < wdev->cqm_config->rssi_thresholds[i])
break;

- low = i > 0 ?
- (wdev->cqm_config->rssi_thresholds[i - 1] - hyst) : S32_MIN;
- high = i < n ?
- (wdev->cqm_config->rssi_thresholds[i] + hyst - 1) : S32_MAX;
+ low_index = i - 1;
+ if (low_index >= 0) {
+ low_index = array_index_nospec(low_index, n);
+ low = wdev->cqm_config->rssi_thresholds[low_index] - hyst;
+ } else {
+ low = S32_MIN;
+ }
+ if (i < n) {
+ i = array_index_nospec(i, n);
+ high = wdev->cqm_config->rssi_thresholds[i] + hyst - 1;
+ } else {
+ high = S32_MAX;
+ }

return rdev_set_cqm_rssi_range_config(rdev, dev, low, high);
}
--
2.17.1