CVE-2022-49613

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> serial: 8250: Fix PM usage_count for console handover<br /> <br /> When console is enabled, univ8250_console_setup() calls<br /> serial8250_console_setup() before .dev is set to uart_port. Therefore,<br /> it will not call pm_runtime_get_sync(). Later, when the actual driver<br /> is going to take over univ8250_console_exit() is called. As .dev is<br /> already set, serial8250_console_exit() makes pm_runtime_put_sync() call<br /> with usage count being zero triggering PM usage count warning<br /> (extra debug for univ8250_console_setup(), univ8250_console_exit(), and<br /> serial8250_register_ports()):<br /> <br /> [ 0.068987] univ8250_console_setup ttyS0 nodev<br /> [ 0.499670] printk: console [ttyS0] enabled<br /> [ 0.717955] printk: console [ttyS0] printing thread started<br /> [ 1.960163] serial8250_register_ports assigned dev for ttyS0<br /> [ 1.976830] printk: console [ttyS0] disabled<br /> [ 1.976888] printk: console [ttyS0] printing thread stopped<br /> [ 1.977073] univ8250_console_exit ttyS0 usage:0<br /> [ 1.977075] serial8250 serial8250: Runtime PM usage count underflow!<br /> [ 1.977429] dw-apb-uart.6: ttyS0 at MMIO 0x4010006000 (irq = 33, base_baud = 115200) is a 16550A<br /> [ 1.977812] univ8250_console_setup ttyS0 usage:2<br /> [ 1.978167] printk: console [ttyS0] printing thread started<br /> [ 1.978203] printk: console [ttyS0] enabled<br /> <br /> To fix the issue, call pm_runtime_get_sync() in<br /> serial8250_register_ports() as soon as .dev is set for an uart_port<br /> if it has console enabled.<br /> <br /> This problem became apparent only recently because 82586a721595 ("PM:<br /> runtime: Avoid device usage count underflows") added the warning<br /> printout. I confirmed this problem also occurs with v5.18 (w/o the<br /> warning printout, obviously).