FAILED: patch "[PATCH] nl80211: validate key indexes for cfg80211_registered_device" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2d9463083ce92636a1bdd3e30d1236e3e95d859e Mon Sep 17 00:00:00 2001
From: Anant Thazhemadam <[email protected]>
Date: Sat, 5 Dec 2020 03:28:25 +0530
Subject: [PATCH] nl80211: validate key indexes for cfg80211_registered_device

syzbot discovered a bug in which an OOB access was being made because an unsuitable key_idx value was wrongly considered to be acceptable while deleting a key in nl80211_del_key().

Since we don't know the cipher at the time of deletion, if cfg80211_validate_key_settings() were to be called directly in nl80211_del_key(), even valid keys would be wrongly determined invalid, and deletion wouldn't occur correctly.
For this reason, a new function - cfg80211_valid_key_idx(), has been created, to determine if the key_idx value provided is valid or not. cfg80211_valid_key_idx() is directly called in 2 places - nl80211_del_key(), and cfg80211_validate_key_settings().

index e3e9686859d4..7df91f940212 100644
@@ -433,6 +433,8 @@ void cfg80211_sme_abandon_assoc(struct wireless_dev *wdev);
 
 /* internal helpers */
 bool cfg80211_supported_cipher_suite(struct wiphy *wiphy, u32 cipher);
+bool cfg80211_valid_key_idx(struct cfg80211_registered_device *rdev,
+			    int key_idx, bool pairwise);
 int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
 				   struct key_params *params, int key_idx,
 				   bool pairwise, const u8 *mac_addr);

index c8d31181a660..910872974f2d 100644
@@ -4239,9 +4239,6 @@ static int nl80211_del_key(struct sk_buff *skb, struct genl_info *info)
 	if (err)
 		return err;
 
-	if (key.idx < 0)
-		return -EINVAL;
-
 	if (info->attrs[NL80211_ATTR_MAC])
 		mac_addr = nla_data(info->attrs[NL80211_ATTR_MAC]);
 

@@ -4257,6 +4254,10 @@ static int nl80211_del_key(struct sk_buff *skb, struct genl_info *info)
 	    key.type != NL80211_KEYTYPE_GROUP)
 		return -EINVAL;
 
+	if (!cfg80211_valid_key_idx(rdev, key.idx,
+				    key.type == NL80211_KEYTYPE_PAIRWISE))
+		return -EINVAL;
+
 	if (!rdev->ops->del_key)
 		return -EOPNOTSUPP;