Vulnerability in Linux Kernel Affects FPSIMD State Management

CVE-2025-38169

What is CVE-2025-38169?

A vulnerability in the Linux kernel related to the management of the Floating Point and SIMD (FPSIMD) state may lead to unintended effects during context switching on systems with Scalable Matrix Extensions (SME). Specifically, when a thread with an FPSIMD state is executed following a thread in streaming Scalable Vector Extensions (SVE) mode, improper handling may cause the kernel FPSIMD state to be overwritten during a context switch. This occurs when the fpsimd_thread_switch() function attempts to restore the FPSIMD state while the CPU remains in streaming SVE mode, resulting in hardware registers being reset and compromising system operations. The issue is addressed by modifying the execution order in the context switch process to ensure the FPSIMD state is appropriately preserved.

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