{"id":"DEBIAN-CVE-2025-38170","details":"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-\u003efpsimd_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-\u003efpsimd_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. This ensures that a subsequent context switch will not reuse the stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the new state to be reloaded from memory prior to a return to userspace.  Note: this was originallly posted as [1].  [ Rutland: rewrite commit message ]","modified":"2026-09-01T16:06:13.891260576Z","published":"2025-07-03T09:15:32.643Z","upstream":["CVE-2025-38170"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-38170"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.147-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-38170.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.35-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-38170.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.35-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-38170.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}