CVE-2022-49841

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

serial: imx: Add missing .thaw_noirq hook

The following warning is seen with non-console UART instance when system hibernates.

[ 37.371969] ------------[ cut here ]------------ [ 37.376599] uart3_root_clk already disabled [ 37.380810] WARNING: CPU: 0 PID: 296 at drivers/clk/clk.c:952 clk_core_disable+0xa4/0xb0 ... [ 37.506986] Call trace: [ 37.509432] clk_core_disable+0xa4/0xb0 [ 37.513270] clk_disable+0x34/0x50 [ 37.516672] imx_uart_thaw+0x38/0x5c [ 37.520250] platform_pm_thaw+0x30/0x6c [ 37.524089] dpm_run_callback.constprop.0+0x3c/0xd4 [ 37.528972] device_resume+0x7c/0x160 [ 37.532633] dpm_resume+0xe8/0x230 [ 37.536036] hibernation_snapshot+0x288/0x430 [ 37.540397] hibernate+0x10c/0x2e0 [ 37.543798] state_store+0xc4/0xd0 [ 37.547203] kobj_attr_store+0x1c/0x30 [ 37.550953] sysfs_kf_write+0x48/0x60 [ 37.554619] kernfs_fop_write_iter+0x118/0x1ac [ 37.559063] new_sync_write+0xe8/0x184 [ 37.562812] vfs_write+0x230/0x290 [ 37.566214] ksys_write+0x68/0xf4 [ 37.569529] __arm64_sys_write+0x20/0x2c [ 37.573452] invoke_syscall.constprop.0+0x50/0xf0 [ 37.578156] do_el0_svc+0x11c/0x150 [ 37.581648] el0_svc+0x30/0x140 [ 37.584792] el0t_64_sync_handler+0xe8/0xf0 [ 37.588976] el0t_64_sync+0x1a0/0x1a4 [ 37.592639] ---[ end trace 56e22eec54676d75 ]---

On hibernating, pm core calls into related hooks in sequence like:

.freeze
.freeze_noirq
.thaw_noirq
.thaw

With .thaw_noirq hook being absent, the clock will be disabled in a unbalanced call which results the warning above.

imx_uart_freeze()
    clk_prepare_enable()
imx_uart_suspend_noirq()
    clk_disable()
imx_uart_thaw
    clk_disable_unprepare()

Adding the missing .thaw_noirq hook as imx_uart_resume_noirq() will have the call sequence corrected as below and thus fix the warning.

imx_uart_freeze()
    clk_prepare_enable()
imx_uart_suspend_noirq()
    clk_disable()
imx_uart_resume_noirq()
    clk_enable()
imx_uart_thaw
    clk_disable_unprepare()

This patch addresses a suspend/hibernate issue in the i.MX UART driver. Without a .thaw_noirq callback, the system ends up disabling clocks in an unbalanced way during resume from hibernation, which causes warnings and could potentially lead to undefined behavior or device instability. The issue is triggered only in specific power management transitions (hibernate), and only non-console UARTs are affected. While it does not present an immediate security risk, it could cause system reliability issues and is notable for embedded platforms using i.MX SoCs.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.