In the Linux kernel, the following vulnerability has been resolved:x86/fpu: Keep xfd_state in sync with MSR_IA32_XFDCommit 672365477ae8 ("x86/fpu: Update XFD state where required") andcommit 8bf26758ca96 ("x86/fpu: Add XFD state to fpstate") introduced aper CPU variable xfd_state to keep the MSR_IA32_XFD value cached, inorder to avoid unnecessary writes to the MSR.On CPU hotplug MSR_IA32_XFD is reset to the init_fpstate.xfd, whichwipes out any stale state. But the per CPU cached xfd value is notreset, which brings them out of sync.As a consequence a subsequent xfd_update_state() might fail to updatethe MSR which in turn can result in XRSTOR raising a #NM in kernelspace, which crashes the kernel.To fix this, introduce xfd_set_state() to write xfd_state togetherwith MSR_IA32_XFD, and use it in all places that set MSR_IA32_XFD.
CWE-416 Use After Free