CVE-2024-46706

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> tty: serial: fsl_lpuart: mark last busy before uart_add_one_port<br /> <br /> With "earlycon initcall_debug=1 loglevel=8" in bootargs, kernel<br /> sometimes boot hang. It is because normal console still is not ready,<br /> but runtime suspend is called, so early console putchar will hang<br /> in waiting TRDE set in UARTSTAT.<br /> <br /> The lpuart driver has auto suspend delay set to 3000ms, but during<br /> uart_add_one_port, a child device serial ctrl will added and probed with<br /> its pm runtime enabled(see serial_ctrl.c).<br /> The runtime suspend call path is:<br /> device_add<br /> |-&gt; bus_probe_device<br /> |-&gt;device_initial_probe<br /> |-&gt;__device_attach<br /> |-&gt; pm_runtime_get_sync(dev-&gt;parent);<br /> |-&gt; pm_request_idle(dev);<br /> |-&gt; pm_runtime_put(dev-&gt;parent);<br /> <br /> So in the end, before normal console ready, the lpuart get runtime<br /> suspended. And earlycon putchar will hang.<br /> <br /> To address the issue, mark last busy just after pm_runtime_enable,<br /> three seconds is long enough to switch from bootconsole to normal<br /> console.