CVE-2025-71119

In the Linux kernel, the following vulnerability has been resolved:

powerpc/kexec: Enable SMT before waking offline CPUs

If SMT is disabled or a partial SMT state is enabled, when a new kernel image is loaded for kexec, on reboot the following warning is observed:

kexec: Waking offline cpu 228. WARNING: CPU: 0 PID: 9062 at arch/powerpc/kexec/core64.c:223 kexecpreparecpus+0x1b0/0x1bc [snip] NIP kexecpreparecpus+0x1b0/0x1bc LR kexecpreparecpus+0x1a0/0x1bc Call Trace: kexecpreparecpus+0x1a0/0x1bc (unreliable) defaultmachinekexec+0x160/0x19c machinekexec+0x80/0x88 kernel_kexec+0xd0/0x118 _dosysreboot+0x210/0x2c4 systemcallexception+0x124/0x320 systemcallvectoredcommon+0x15c/0x2ec

This occurs as addcpu() fails due to cpubootable() returning false for CPUs that fail the cpusmtthread_allowed() check or non primary threads if SMT is disabled.

Fix the issue by enabling SMT and resetting the number of SMT threads to the number of threads per core, before attempting to wake up all present CPUs.