CVE-2025-38170 — arm64/fpsimd: Discard stale CPU state when handling SME traps

Affected: Linux

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

arm64/fpsimd: Discard stale CPU state when handling SME traps

The logic for handling SME traps manipulates saved FPSIMD/SVE/SME state incorrectly, and a race with preemption can result in a task having TIF_SME set and TIF_FOREIGN_FPSTATE clear even though the live CPU state is stale (e.g. with SME traps enabled). This can result in warnings from do_sme_acc() where SME traps are not expected while TIF_SME is set:

| /* With TIF_SME userspace shouldn't generate any traps */ | if (test_and_set_thread_flag(TIF_SME)) | WARN_ON(1);

This is very similar to the SVE issue we fixed in commit:

751ecf6afd6568ad ("arm64/sve: Discard stale CPU state when handling SVE traps")

The race can occur when the SME trap handler is preempted before and after manipulating the saved FPSIMD/SVE/SME state, starting and ending on the same CPU, e.g.

| void do_sme_acc(unsigned long esr, struct pt_regs *regs) | { | // Trap on CPU 0 with TIF_SME clear, SME traps enabled | // task->fpsimd_cpu is 0. | // per_cpu_ptr(&fpsimd_last_state, 0) is task. | | ... | | // Preempted; migrated from CPU 0 to CPU 1. | // TIF_FOREIGN_FPSTATE is set. | | get_cpu_fpsimd_context(); | | /* With TIF_SME userspace shouldn't generate any traps */ | if (test_and_set_thread_flag(TIF_SME)) | WARN_ON(1); | | if (!test_thread_flag(TIF_FOR…

USN-7769-1 — linux, linux-aws, linux-gcp, linux-gcp-6.14, linux-oracle, linux-realtime vulnerabilities

Affected: Ubuntu:24.04:LTS: linux-gcp-6.14

Several security issues were discovered in the Linux kernel. An attacker could possibly use these to compromise the system. This update corrects flaws in the following subsystems: - ARM64 architecture; - PowerPC architecture; - x86 architecture; - Block layer subsystem; - Cryptographic API; - ACPI drivers; - Android drivers; - Bluetooth drivers; - Bus devices; - Clock framework and drivers; - CPU frequency scaling framework; - Hardware crypto device drivers; - DMA engine subsystem; - EDAC drivers; - Arm Firmware Framework for ARMv8-A(FFA); - FPGA Framework; - GPIO subsystem; - GPU drivers; - HID subsystem; - Hardware monitoring drivers; - HW tracing; - InfiniBand drivers; - IOMMU subsystem; - Multiple devices driver; - Media drivers; - VMware VMCI Driver; - MTD block device drivers; - Network drivers; - Mellanox network drivers; - STMicroelectronics network drivers; - NVDIMM (Non-Volatile Memory Device) drivers; - NVME drivers; - NVMEM (Non Volatile Memory) drivers; - PCI subsystem; - Amlogic Meson DDR PMU; - NI-700 PMU driver; - PHY drivers; - Pin controllers subsystem; - x86 platform drivers; - PTP clock framework; - SCSI subsystem; - ASPEED SoC drivers; - SPI subsystem; - TCM subsystem; - Thunderbolt and USB4 drivers; - TTY drivers; - UFS subsystem; - USB core drivers; - USB Gadget drivers; - Renesas USBHS Controller drivers; - USB Type-C Port Controller Manager driver;…

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CVE-2025-38170 — arm64/fpsimd: Discard stale CPU state when handling SME traps

USN-7769-1 — linux, linux-aws, linux-gcp, linux-gcp-6.14, linux-oracle, linux-realtime vulnerabilities