[PATCH] wifi: nl80211: don't WARN on a missing self-managed regdom

["François Roux" <franzelfranzel@gmail.com>]

nl80211_get_reg_do() has a WARN_ON() for a self-managed wiphy without a
private regdomain. Userspace can trigger it with a plain
NL80211_CMD_GET_REG request.

Drivers can register such a wiphy first and set its regdomain later.
ath12k, for example, calls ieee80211_register_hw() and only then applies
the regdomain with ath12k_regd_update(). iwd queries the regdomain of a
new wiphy as soon as it shows up, so it can hit that window at boot:

  WARNING: net/wireless/nl80211.c:10828 at nl80211_get_reg_do+0x1d0/0x1fc [cfg80211], CPU#5: iwd/721
  Call trace:
   nl80211_get_reg_do+0x1d0/0x1fc [cfg80211] (P)
   genl_family_rcv_msg_doit+0xd0/0x138
   genl_rcv_msg+0x58/0xd4
   netlink_rcv_skb+0x5c/0x140
   genl_rcv+0x34/0x4c
   netlink_unicast+0x31c/0x39c
   netlink_sendmsg+0x188/0x400

The same trace has been reported with an Intel BE200 (iwlwifi). The dump
variant, nl80211_get_reg_dump(), already skips a wiphy without a
regdomain without warning.

Keep returning -EINVAL, but drop the WARN_ON(). The same change was
posted in 2021 but was never applied.

Seen on a Microsoft Surface Pro 11 (WCN7850, ath12k) in 3 of 4 boots
with next-20260929.

Fixes: 1bdd716cbcca ("cfg80211: return private regdom for self-managed devices")
Reported-by: Diederik de Haas <diederik@cknow-tech.com>
Closes: https://lore.kernel.org/all/DL5P72WYQVOQ.23G9D01OY3BAA@cknow-tech.com/
Link: https://lore.kernel.org/all/iwlwifi.20210409123755.ba2ea961f4ae.I8fde32d3196e860efa3b4ec464c42194195b42ec@changeid/
Assisted-by: LLM
Signed-off-by: François Roux <franzelfranzel@gmail.com>
---
 net/wireless/nl80211.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index a18240455..2589491af 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -10824,8 +10824,12 @@ static int nl80211_get_reg_do(struct sk_buff *skb, struct genl_info *info)
 
 		regdom = get_wiphy_regdom(wiphy);
 
-		/* a self-managed-reg device must have a private regdom */
-		if (WARN_ON(!regdom && self_managed)) {
+		/*
+		 * A self-managed-reg device gets its private regdom from the
+		 * driver, which may happen only after the wiphy is registered.
+		 * Userspace can ask before that, so don't WARN.
+		 */
+		if (!regdom && self_managed) {
 			err = -EINVAL;
 			goto nla_put_failure_rcu;
 		}

base-commit: 6474fa070f2b8013b4b87350b775b8c3be6e8aac
-- 
2.56.0