wifi: mac80211: prohibit deactivating all links

In the internal API this calls this is a WARN_ON, but that
should remain since internally we want to know about bugs
that may cause this. Prevent deactivating all links in the
debugfs write directly.

Reported-by: syzbot+0c5d8e65f23569a8ffec@syzkaller.appspotmail.com
Fixes: 3d9011029227 ("wifi: mac80211: implement link switching")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://patch.msgid.link/20241230091408.505bd125c35a.Ic3c1f9572b980a952a444cad62b09b9c6721732b@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index a9bc2fd59f55ad3b1efec7f47d499fbeb4448584..e7687a7b16835ab851af4ed7fc255d17ebc25e32 100644 (file)
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -727,7 +727,7 @@ static ssize_t ieee80211_if_parse_active_links(struct ieee80211_sub_if_data *sda
 {
        u16 active_links;
 
-       if (kstrtou16(buf, 0, &active_links))
+       if (kstrtou16(buf, 0, &active_links) || !active_links)
                return -EINVAL;
 
        return ieee80211_set_active_links(&sdata->vif, active_links) ?: buflen;