CVE-2021-47429

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> powerpc/64s: Fix unrecoverable MCE calling async handler from NMI<br /> <br /> The machine check handler is not considered NMI on 64s. The early<br /> handler is the true NMI handler, and then it schedules the<br /> machine_check_exception handler to run when interrupts are enabled.<br /> <br /> This works fine except the case of an unrecoverable MCE, where the true<br /> NMI is taken when MSR[RI] is clear, it can not recover, so it calls<br /> machine_check_exception directly so something might be done about it.<br /> <br /> Calling an async handler from NMI context can result in irq state and<br /> other things getting corrupted. This can also trigger the BUG at<br /> arch/powerpc/include/asm/interrupt.h:168<br /> BUG_ON(!arch_irq_disabled_regs(regs) &amp;&amp; !(regs-&gt;msr &amp; MSR_EE));<br /> <br /> Fix this by making an _async version of the handler which is called<br /> in the normal case, and a NMI version that is called for unrecoverable<br /> interrupts.