From 4052d3d2e8f47a15053320bbcbe365d15610437d Mon Sep 17 00:00:00 2001
From: Julian Squires <julian@cipht.net>
Date: Mon, 6 Jul 2020 17:13:53 -0400
Subject: [PATCH] cfg80211: check vendor command doit pointer before use
Git-commit: 4052d3d2e8f47a15053320bbcbe365d15610437d
Patch-mainline: v5.8
References: git-fixes

In the case where a vendor command does not implement doit, and has no
flags set, doit would not be validated and a NULL pointer dereference
would occur, for example when invoking the vendor command via iw.

I encountered this while developing new vendor commands.  Perhaps in
practice it is advisable to always implement doit along with dumpit,
but it seems reasonable to me to always check doit anyway, not just
when NEED_WDEV.

Signed-off-by: Julian Squires <julian@cipht.net>
Link: https://lore.kernel.org/r/20200706211353.2366470-1-julian@cipht.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 net/wireless/nl80211.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 0e07fb8585fb..7fbca0854265 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -13266,13 +13266,13 @@ static int nl80211_vendor_cmd(struct sk_buff *skb, struct genl_info *info)
 				if (!wdev_running(wdev))
 					return -ENETDOWN;
 			}
-
-			if (!vcmd->doit)
-				return -EOPNOTSUPP;
 		} else {
 			wdev = NULL;
 		}
 
+		if (!vcmd->doit)
+			return -EOPNOTSUPP;
+
 		if (info->attrs[NL80211_ATTR_VENDOR_DATA]) {
 			data = nla_data(info->attrs[NL80211_ATTR_VENDOR_DATA]);
 			len = nla_len(info->attrs[NL80211_ATTR_VENDOR_DATA]);
-- 
2.16.4