In the Linux kernel, the following vulnerability has been resolved: x86/fpu: Ensure XFD state on signal delivery Sean reported [1] the following splat when running KVM tests: WARNING: CPU: 232 PID: 15391 at xfdvalidatestate+0x65/0x70 Call Trace: <TASK> fpuclearuserstates+0x9c/0x100 archdosignalorrestart+0x142/0x210 exittousermodeloop+0x55/0x100 dosyscall64+0x205/0x2c0 entrySYSCALL64afterhwframe+0x4b/0x53 Chao further identified [2] a reproducible scenario involving signal delivery: a non-AMX task is preempted by an AMX-enabled task which modifies the XFD MSR. When the non-AMX task resumes and reloads XSTATE with init values, a warning is triggered due to a mismatch between fpstate::xfd and the CPU's current XFD state. fpuclearuserstates() does not currently re-synchronize the XFD state after such preemption. Invoke xfdupdatestate() which detects and corrects the mismatch if there is a dynamic feature. This also benefits the sigreturn path, as fpurestoresig() may call fpuclearuser_states() when the sigframe is inaccessible. [ dhansen: minor changelog munging ]