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CVE-2025-38170
published 2025-07-03

CVE-2025-38170: 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…

medium5.5CVSS 3.1
AVLACLPRLUINSUCNINAH
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_FOREIGN_FPSTATE)) { | unsigned long vq_minus_one = | sve_vq_from_vl(task_get_sme_vl(current)) - 1; | sme_set_vq(vq_minus_one); | | fpsimd_bind_task_to_cpu(); | } | | put_cpu_fpsimd_context(); | | // Preempted; migrated from CPU 1 to CPU 0. | // task->fpsimd_cpu is still 0 | // If per_cpu_ptr(&fpsimd_last_state, 0) is still task then: | // - Stale HW state is reused (with SME traps enabled) | // - TIF_FOREIGN_FPSTATE is cleared | // - A return to userspace skips HW state restore | } Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set by calling fpsimd_flush_task_state() to detach from the saved CPU state

Affected

28 ranges· showing 25
VendorProductVersion rangeFixed in
debiandebian_linux
debianlinux< linux 6.1.147-1 (bookworm)linux 6.1.147-1 (bookworm)
debianlinux-6.1< linux 6.1.147-1 (bookworm)linux 6.1.147-1 (bookworm)
linuxlinux
linuxlinux>= 8bd7f91c03d886f41d35f6108078d20be5a4a1bd < de89368de3894a8db27caeb8fd902ba1c49f696ade89368de3894a8db27caeb8fd902ba1c49f696a
linuxlinux>= 8bd7f91c03d886f41d35f6108078d20be5a4a1bd < 43be952e885476dafb74aa832c0847b2f4f650c643be952e885476dafb74aa832c0847b2f4f650c6
linuxlinux>= 8bd7f91c03d886f41d35f6108078d20be5a4a1bd < 6103f9ba51a59afb5a0f32299c837377c5a5a6936103f9ba51a59afb5a0f32299c837377c5a5a693
linuxlinux>= 8bd7f91c03d886f41d35f6108078d20be5a4a1bd < c4a4786d93e99517d6f10ed56b9ffba4ce88d3b3c4a4786d93e99517d6f10ed56b9ffba4ce88d3b3
linuxlinux>= 8bd7f91c03d886f41d35f6108078d20be5a4a1bd < d3eaab3c70905c5467e5c4ea403053d67505adebd3eaab3c70905c5467e5c4ea403053d67505adeb
linuxlinux_kernel>= 0 < 6.1.147-16.1.147-1
linuxlinux_kernel>= 0 < 6.12.35-16.12.35-1
linuxlinux_kernel>= 0 < 6.12.35-16.12.35-1
linuxlinux_kernel>= 0 < 6.8.0-100.1006.8.0-100.100
linuxlinux_kernel>= 5.19 < 6.1.1426.1.142
linuxlinux_kernel>= 6.13 < 6.15.36.15.3
linuxlinux_kernel>= 6.2 < 6.6.946.6.94
linuxlinux_kernel>= 6.7 < 6.12.346.12.34
msrcazl3_kernel_6.6.92.2-2_on_azure_linux_3.0
msrcazl3_kernel_6.6.96.1-1_on_azure_linux_3.0
ubuntulinux-aws
ubuntulinux-aws-6.8
ubuntulinux-gkeop
ubuntulinux-nvidia
ubuntulinux-nvidia-6.8
ubuntulinux-oracle

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
osv5.5MEDIUM
CVE-2025-38170 — Resource Injection in Linux | cvebase