CVE-2025-38169

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

arm64/fpsimd: Avoid clobbering kernel FPSIMD state with SMSTOP

On system with SME, a thread's kernel FPSIMD state may be erroneously

clobbered during a context switch immediately after that state is

restored. Systems without SME are unaffected.

If the CPU happens to be in streaming SVE mode before a context switch

to a thread with kernel FPSIMD state, fpsimd_thread_switch() will

restore the kernel FPSIMD state using fpsimd_load_kernel_state() while

the CPU is still in streaming SVE mode. When fpsimd_thread_switch()

subsequently calls fpsimd_flush_cpu_state(), this will execute an

SMSTOP, causing an exit from streaming SVE mode. The exit from

streaming SVE mode will cause the hardware to reset a number of

FPSIMD/SVE/SME registers, clobbering the FPSIMD state.

Fix this by calling fpsimd_flush_cpu_state() before restoring the kernel

FPSIMD state.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References