CVE-2022-49841 is a vulnerability in the Linux kernel specifically related to the imx UART serial driver. The issue arises from a missing .thaw_noirq hook in the power management (pm) core sequence for handling system hibernation and resume operations. During hibernation, the pm core calls a series of hooks in the following order: .freeze, .freeze_noirq, .thaw_noirq, and .thaw. The imx UART driver implements .freeze, .freeze_noirq, and .thaw hooks but lacks the .thaw_noirq hook, which leads to an unbalanced clock disable call sequence. This manifests as a warning message during system resume from hibernation, indicating that the uart3_root_clk is already disabled and triggering a kernel warning and call trace. The root cause is that the clock disable/enable calls are not properly balanced due to the missing .thaw_noirq hook, which should re-enable the clock before the final .thaw disables and unprepares it. The fix involves adding the missing .thaw_noirq hook (imx_uart_resume_noirq) to correctly balance the clock enable/disable calls during the resume process. This correction prevents the kernel warnings and potential instability during hibernation resume cycles. The vulnerability does not appear to allow direct code execution or privilege escalation but may cause system instability or kernel warnings that could impact system reliability. The affected versions are specific Linux kernel commits identified by their hashes, indicating this is a low-level kernel driver issue. No known exploits are reported in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of this vulnerability is primarily related to system stability and reliability rather than direct security compromise. Systems using affected Linux kernel versions with imx UART drivers—commonly found in embedded devices, industrial control systems, and specialized hardware platforms—may experience kernel warnings or potential crashes during hibernation or suspend/resume cycles. This could lead to unexpected downtime or degraded performance in critical infrastructure, manufacturing environments, or IoT deployments. While it does not directly expose confidentiality or integrity risks, the instability could indirectly affect availability of services relying on these systems. Organizations with embedded Linux devices in sectors such as automotive, telecommunications, or industrial automation in Europe should be aware of this issue. The lack of known exploits reduces immediate risk, but unaddressed kernel warnings could complicate system maintenance and troubleshooting, especially in large-scale deployments.

To mitigate this vulnerability, organizations should apply the patch that adds the missing .thaw_noirq hook (imx_uart_resume_noirq) to the imx UART driver in the Linux kernel. This requires updating to a fixed kernel version or backporting the patch if using long-term support kernels. System administrators should verify the kernel version and confirm if the affected commits are present. For embedded or specialized devices, coordinate with hardware vendors or Linux distribution maintainers to obtain updated firmware or kernel packages. Additionally, monitoring system logs for the specific kernel warning messages related to uart3_root_clk during hibernation can help identify affected systems. Avoid relying on hibernation or suspend/resume features on impacted devices until patched, if feasible. Implementing robust kernel update procedures and testing power management features post-update will ensure stability. Since this is a low-level kernel driver issue, generic mitigations like disabling UART devices are impractical; the focus should be on timely patching and system monitoring.