CVE-2022-50820: 
Linux Kernel vulnerability analysis and mitigation

CVE-2022-50820 is a resource leak vulnerability in the Linux kernel's perf/arm_dmc620 driver, specifically a hotplug callback leak in the dmc620_pmu_init() function. When platform_driver_register() fails, the callback registered via cpuhp_setup_state_multi() is not properly removed, resulting in a dangling callback registration. The vulnerability affects Linux kernel versions from 5.11 up to the patched releases (5.15.86, 6.0.16, 6.1.2, and 6.2). It was published on December 30, 2025, with a CVSS base score of 0.0 and an EPSS score of 0.000180, indicating very low exploitability (Feedly, EUVD).

The root cause is improper resource cleanup (CWE-459: Incomplete Cleanup) in the dmc620_pmu_init() function within the Linux kernel's ARM DMC-620 PMU driver. When platform_driver_register() returns an error, the function exits without calling cpuhp_remove_multi_state() to deregister the CPU hotplug callback previously set up by cpuhp_setup_state_multi(). This leaves a stale callback registered in the hotplug state machine, which could lead to use-after-free or undefined behavior if the hotplug subsystem later invokes the leaked callback. The fix mirrors the approach used in commit 26242b330093 for arm_ccn_init() (Feedly, Kernel Patch).

The primary impact is a kernel-level resource leak that could result in system instability or undefined behavior during CPU hotplug operations on ARM systems using the DMC-620 memory controller PMU. In a worst-case scenario, the stale callback could be invoked after the associated driver state has been freed, potentially leading to a kernel panic or memory corruption. The vulnerability is limited to systems with the ARM DMC-620 hardware and does not directly expose user data or allow remote code execution (Feedly).

The fix has been backported to stable Linux kernel releases: 5.15.86, 6.0.16, 6.1.2, and 6.2. Users should update their Linux kernel to one of these patched versions or later. The fix adds a call to cpuhp_remove_multi_state() in the error path of dmc620_pmu_init() to properly clean up the hotplug callback on failure. No configuration-based workaround is available; upgrading the kernel is the recommended remediation (Feedly, Kernel Patch).