CVE-2022-20153 in Android
Summary
by MITRE • 06/15/2022
In rcu_cblist_dequeue of rcu_segcblist.c, there is a possible use-after-free due to improper locking. This could lead to local escalation of privilege in the kernel with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-222091980References: Upstream kernel
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Analysis
by VulDB Data Team • 05/18/2025
The vulnerability identified as CVE-2022-20153 resides within the Linux kernel's RCU (Read-Copy-Update) subsystem, specifically in the rcu_cblist_dequeue function located in rcu_segcblist.c. This represents a critical use-after-free condition that arises from inadequate locking mechanisms during concurrent access to RCU callback lists. The flaw manifests when multiple threads attempt to manipulate callback lists without proper synchronization, creating a window where freed memory can be accessed and potentially reused by subsequent operations. Such improper locking allows for memory corruption that can be exploited to gain elevated privileges within the kernel space.
The technical implementation of this vulnerability stems from the RCU subsystem's design for handling callback functions that are executed after read-side critical sections complete. When the rcu_cblist_dequeue function processes callback entries, it fails to maintain proper atomicity during list manipulation operations. The absence of appropriate mutex or spinlock protection during the dequeue operation creates a race condition where one thread may free a callback structure while another thread attempts to access it. This use-after-free scenario falls under CWE-416, which specifically addresses the use of memory after it has been freed, and can be classified as a kernel-level memory corruption vulnerability.
The operational impact of this vulnerability extends to local privilege escalation within the Android kernel environment, requiring only system execution privileges for exploitation. Attackers can leverage this flaw to execute arbitrary code with kernel-level privileges, potentially compromising the entire system. The vulnerability's exploitation does not require user interaction, making it particularly dangerous as it can be triggered automatically during normal system operation. This characteristic aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities, and represents a significant threat to Android device security where kernel-level attacks can bypass traditional user-space protections.
Mitigation strategies for CVE-2022-20153 primarily focus on implementing proper locking mechanisms within the RCU subsystem. The most effective approach involves adding appropriate synchronization primitives such as mutexes or spinlocks around the critical sections of the rcu_cblist_dequeue function to ensure atomic access to callback lists. Additionally, kernel updates and patches addressing this specific race condition should be deployed immediately, as the upstream kernel has already provided fixes for this vulnerability. System administrators should also consider implementing kernel hardening measures including stack canaries, kernel address space layout randomization, and control flow integrity checks to reduce the overall attack surface. The Android security team has assigned this vulnerability the identifier A-222091980, indicating its severity and the need for immediate remediation across affected Android kernel versions.