CVE-2024-35801: x86/fpu: Keep xfd_state in sync with MSR_IA32_XFD

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-17 · updated 2026-06-17
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: x86/fpu: Keep xfd_state in sync with MSR_IA32_XFD Commit 672365477ae8 ("x86/fpu: Update XFD state where required") and commit 8bf26758ca96 ("x86/fpu: Add XFD state to fpstate") introduced a per CPU variable xfd_state to keep the MSR_IA32_XFD value cached, in order to avoid unnecessary writes to the MSR. On CPU hotplug MSR_IA32_XFD is reset to the init_fpstate.xfd, which wipes out any stale state. But the per CPU cached xfd value is not reset, which brings them out of sync. As a consequence a subsequent xfd_update_state() might fail to update the MSR which in turn can result in XRSTOR raising a #NM in kernel space, which crashes the kernel. To fix this, introduce xfd_set_state() to write xfd_state together with MSR_IA32_XFD, and use it in all places that set MSR_IA32_XFD.

Affected products

Linux kernel: from 5.16 before 6.1.84; from 6.2 before 6.6.24; from 6.7 before 6.7.12; from 6.8 before 6.8.3 — fixed in 6.1.84, 6.6.24, 6.7.12, 6.8.3

How to fix

Upgrade to a fixed version: Linux kernel 6.1.84, 6.6.24, 6.7.12, 6.8.3. Check the vendor advisory for mitigations.

References

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