[PATCH 11/32] nl80211: Use mem_to_flex_dup() with struct cfg80211_cqm_config

[Kees Cook]

As part of the work to perform bounds checking on all memcpy() uses,
replace the open-coded a deserialization of bytes out of memory into a
trailing flexible array by using a flex_array.h helper to perform the
allocation, bounds checking, and copying.

Cc: Johannes Berg <johannes at sipsolutions.net>
Cc: "David S. Miller" <davem at davemloft.net>
Cc: Jakub Kicinski <kuba at kernel.org>
Cc: Paolo Abeni <pabeni at redhat.com>
Cc: linux-wireless at vger.kernel.org
Cc: netdev at vger.kernel.org
Cc: Eric Dumazet <edumazet at google.com>
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 net/wireless/core.h    |  4 ++--
 net/wireless/nl80211.c | 15 ++++-----------
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/net/wireless/core.h b/net/wireless/core.h
index 3a7dbd63d8c6..899d111993c6 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -295,8 +295,8 @@ struct cfg80211_beacon_registration {
 struct cfg80211_cqm_config {
 	u32 rssi_hyst;
 	s32 last_rssi_event_value;
-	int n_rssi_thresholds;
-	s32 rssi_thresholds[];
+	DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(int, n_rssi_thresholds);
+	DECLARE_FLEX_ARRAY_ELEMENTS(s32, rssi_thresholds);
 };
 
 void cfg80211_destroy_ifaces(struct cfg80211_registered_device *rdev);
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 945ed87d12e0..70df7132cce8 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -12096,21 +12096,14 @@ static int nl80211_set_cqm_rssi(struct genl_info *info,
 
 	wdev_lock(wdev);
 	if (n_thresholds) {
-		struct cfg80211_cqm_config *cqm_config;
+		struct cfg80211_cqm_config *cqm_config = NULL;
 
-		cqm_config = kzalloc(struct_size(cqm_config, rssi_thresholds,
-						 n_thresholds),
-				     GFP_KERNEL);
-		if (!cqm_config) {
-			err = -ENOMEM;
+		err = mem_to_flex_dup(&cqm_config, thresholds, n_thresholds,
+				      GFP_KERNEL);
+		if (err)
 			goto unlock;
-		}
 
 		cqm_config->rssi_hyst = hysteresis;
-		cqm_config->n_rssi_thresholds = n_thresholds;
-		memcpy(cqm_config->rssi_thresholds, thresholds,
-		       flex_array_size(cqm_config, rssi_thresholds,
-				       n_thresholds));
 
 		wdev->cqm_config = cqm_config;
 	}
-- 
2.32.0