From: Johannes Berg <johannes.berg@intel.com>
Date: Fri, 21 Nov 2025 10:37:34 +0000 (+0100)
Subject: wifi: mac80211: fix channel switching code
X-Git-Tag: v6.19-rc1~170^2~33^2~9
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=de3c5142349c6cd67fbd20afc5b3ae320df436b7;p=thirdparty%2Fkernel%2Flinux.git

wifi: mac80211: fix channel switching code

My prior commit here introduced a bug due to copy/paste,
it was iterating the links assigned to 'ctx->replace_ctx'
and I replaced it by iterating links assigned to 'ctx' by
accident, then modified it for the iteration later.

Fix it to iterate the users of the correct chanctx, i.e.
'ctx->replace_ctx'.

Ultimately, this issue led to a crash in a hwsim test
(multi_ap_wps_shared_apdev_csa) because it would actually
do the switch (rather than refuse here) and then later
have a double-free of the original chanctx, because it
was still in use by another interface yet freed as part
of the switching.

Fixes: a1dc648aa76d ("wifi: mac80211: remove chanctx to link back-references")
Link: https://patch.msgid.link/20251121113733.7710a58d45eb.Ie9ec010b52b1baed93dbe44f968c2119b6b5d98d@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index 6aa305839f534..c8aba4183c9a2 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -1715,7 +1715,7 @@ static int ieee80211_vif_use_reserved_switch(struct ieee80211_local *local)
 		n_reserved = 0;
 		n_ready = 0;
 
-		for_each_chanctx_user_assigned(local, ctx, &iter) {
+		for_each_chanctx_user_assigned(local, ctx->replace_ctx, &iter) {
 			n_assigned++;
 			if (iter.link->reserved_chanctx) {
 				n_reserved++;