Memory Management Flaw in Linux Kernel Impacting Tracer Hash Functionality

CVE-2025-39689

What is CVE-2025-39689?

A memory management flaw exists in the Linux kernel related to the handling of tracer hashes within the ftrace subsystem. The vulnerability allows for an improper allocation of pointers when reading filter files, leading to potential use-after-free conditions. Unlike writers that correctly allocate copies of the hash for their iterators, the reader maintains a static pointer. This discrepancy poses risks during function calls that release locks, as the global tracer hashes can be updated unexpectedly. The recent fix enhances the code by ensuring a proper allocation and copy of the hash for readers, thus mitigating these risks and streamlining the overall code structure.

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