Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

wifi: mwifiex: fix permanently busy scans after multiple roam iterations

In order for the firmware to sleep, the driver has to confirm a previously received sleep request. The normal sequence of evets goes like this: EVENT_SLEEP -> adapter->ps_state = PS_STATE_PRE_SLEEP -> sleep-confirm -> SLEEP -> EVENT_AWAKE -> AWAKE. Before sending the sleep-confirm command, the driver must make sure there are no commands either running or waiting to be completed.

mwifiex_ret_802_11_associate() unconditionally sets ps_state = PS_STATE_AWAKE when it processes the association command response, outside of the normal powersave management flow. If EVENT_SLEEP arrives while the association command is in flight, ps_state is PRE_SLEEP when the association command response is parsed, and the forced AWAKE overwrites it. The deferred sleep-confirm is never sent.

A subsequent scan_start command is correctly acknowledged, but the firmware doesn't generate scan_result events. The scan request never finishes, and additional requests from userspace fail with -EBUSY.

After testing on both IW412 and W8997, I could only trigger the bug on the IW412 and observed the firmwares behave differently. On the IW412 the firmware still sends EVENT_SLEEP while the authentication / association process is ongoing. A W8997 under the same conditions seems to suppress power-save for the duration of the association, so PRE_SLEEP never coincided with th…