Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:[EOL][EOL]x86/fpu: Ensure XFD state on signal delivery[EOL][EOL]Sean reported [1] the following splat when running KVM tests:[EOL][EOL]   WARNING: CPU: 232 PID: 15391 at xfd_validate_state+0x65/0x70[EOL]   Call Trace:[EOL]    <TASK>[EOL]    fpu__clear_user_states+0x9c/0x100[EOL]    arch_do_signal_or_restart+0x142/0x210[EOL]    exit_to_user_mode_loop+0x55/0x100[EOL]    do_syscall_64+0x205/0x2c0[EOL]    entry_SYSCALL_64_after_hwframe+0x4b/0x53[EOL][EOL]Chao further identified [2] a reproducible scenario involving signal[EOL]delivery: a non-AMX task is preempted by an AMX-enabled task which[EOL]modifies the XFD MSR.[EOL][EOL]When the non-AMX task resumes and reloads XSTATE with init values,[EOL]a warning is triggered due to a mismatch between fpstate::xfd and the[EOL]CPU's current XFD state. fpu__clear_user_states() does not currently[EOL]re-synchronize the XFD state after such preemption.[EOL][EOL]Invoke xfd_update_state() which detects and corrects the mismatch if[EOL]there is a dynamic feature.[EOL][EOL]This also benefits the sigreturn path, as fpu__restore_sig() may call[EOL]fpu__clear_user_states() when the sigframe is inaccessible.[EOL][EOL][ dhansen: minor changelog munging ]