[PATCH RESEND wireless 04/10] wifi: mac80211: don't allow link changes when iface is down

[Johannes Berg <johannes@sipsolutions.net>]

From: Johannes Berg <johannes.berg@intel.com>

ieee80211_set_active_links() only checks that the interface is running in
the inner __ieee80211_set_active_links(), after drv_can_activate_links()
was already called, so using active_links on an interface that's down
triggers the check-sdata-in-driver warning.

Add the missing check in the debugfs file.

Assisted-by: LLM
Fixes: 3d9011029227 ("wifi: mac80211: implement link switching")
Reported-by: syzbot+582469b3a9ef5f13606b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=582469b3a9ef5f13606b
Link: https://patch.msgid.link/20260904170057.56ab694fe989.I6d85e530bc2db6e48bfd13ccee0b71155e32b85b@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/debugfs_netdev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index f3c6a41e4911..8346d3eb1143 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -729,6 +729,9 @@ static ssize_t ieee80211_if_parse_active_links(struct ieee80211_sub_if_data *sda
 	if (kstrtou16(buf, 0, &active_links) || !active_links)
 		return -EINVAL;
 
+	if (!ieee80211_sdata_running(sdata))
+		return -ENETDOWN;
+
 	return ieee80211_set_active_links(&sdata->vif, active_links) ?: buflen;
 }
 IEEE80211_IF_FILE_RW(active_links);
-- 
2.55.0