CVE-2021-47225

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> mac80211: fix deadlock in AP/VLAN handling<br /> <br /> Syzbot reports that when you have AP_VLAN interfaces that are up<br /> and close the AP interface they belong to, we get a deadlock. No<br /> surprise - since we dev_close() them with the wiphy mutex held,<br /> which goes back into the netdev notifier in cfg80211 and tries to<br /> acquire the wiphy mutex there.<br /> <br /> To fix this, we need to do two things:<br /> 1) prevent changing iftype while AP_VLANs are up, we can&amp;#39;t<br /> easily fix this case since cfg80211 already calls us with<br /> the wiphy mutex held, but change_interface() is relatively<br /> rare in drivers anyway, so changing iftype isn&amp;#39;t used much<br /> (and userspace has to fall back to down/change/up anyway)<br /> 2) pull the dev_close() loop over VLANs out of the wiphy mutex<br /> section in the normal stop case