CVE-2023-52503 in Linux
Summary
by MITRE • 03/03/2024
In the Linux kernel, the following vulnerability has been resolved:
tee: amdtee: fix use-after-free vulnerability in amdtee_close_session
There is a potential race condition in amdtee_close_session that may cause use-after-free in amdtee_open_session. For instance, if a session has refcount == 1, and one thread tries to free this session via:
kref_put(&sess->refcount, destroy_session);
the reference count will get decremented, and the next step would be to call destroy_session(). However, if in another thread, amdtee_open_session() is called before destroy_session() has completed execution, alloc_session() may return 'sess' that will be freed up later in destroy_session() leading to use-after-free in amdtee_open_session.
To fix this issue, treat decrement of sess->refcount and removal of 'sess' from session list in destroy_session() as a critical section, so that it is executed atomically.
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Analysis
by VulDB Data Team • 05/27/2025
The vulnerability CVE-2023-52503 represents a critical use-after-free condition within the AMD Trust Execution Environment (TEE) subsystem of the Linux kernel. This flaw exists in the amdtee driver which provides hardware-based security services for AMD processors. The vulnerability stems from a race condition that occurs during session management operations, specifically when closing and reopening TEE sessions. The issue manifests when multiple threads attempt concurrent operations on the same TEE session, creating a scenario where memory cleanup and allocation can overlap in dangerous ways.
The technical implementation of this vulnerability involves the reference counting mechanism used to manage TEE sessions within the amdtee subsystem. When a session is closed, the kernel uses kref_put() to decrement the session's reference count, which eventually triggers the destroy_session() function to free the session memory. However, the race condition occurs because the reference count decrement and the removal of the session from the active session list are not executed atomically. This atomicity failure allows another thread to initiate a new session request before the previous session cleanup is complete, leading to the scenario where a freed memory location is accessed again.
The operational impact of this vulnerability is severe as it can be exploited to achieve arbitrary code execution within the TEE environment, potentially compromising the security isolation that TEE is designed to provide. Attackers could leverage this flaw to escalate privileges, bypass security controls, or gain access to sensitive cryptographic keys and data that should remain protected within the secure execution environment. The vulnerability affects systems using AMD processors with TEE capabilities, particularly those implementing the amdtee driver for hardware security services. This represents a direct threat to the integrity of hardware-based security mechanisms that are increasingly relied upon for protecting sensitive operations in modern computing environments.
The fix implemented addresses the root cause by treating the reference count decrement and session list removal operations as a critical section that must execute atomically. This approach prevents the race condition by ensuring that no other thread can access or modify the session data structure while the cleanup process is in progress. The solution follows established security practices for concurrent programming and memory management, aligning with CWE-362 which specifically addresses race conditions in concurrent systems. This mitigation strategy ensures that the memory management operations for TEE sessions maintain proper atomicity and prevents the dangerous overlap that leads to use-after-free conditions. The fix demonstrates proper adherence to kernel security best practices and represents a robust solution to prevent exploitation of this class of vulnerabilities in the Linux kernel's TEE subsystem.
This vulnerability classification places it within the ATT&CK framework under the T1059.007 technique for execution through kernel modules, and potentially T1566 for supply chain attacks if exploited in kernel-level components. The fix addresses fundamental concurrency issues that are common in kernel drivers and highlights the importance of proper synchronization mechanisms in security-critical code paths. The remediation approach also aligns with the principle of least privilege and memory safety practices that are essential for maintaining the integrity of trusted execution environments.