CVE-2022-50870

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

powerpc/rtas: avoid device tree lookups in rtasosterm()

rtasosterm() is called during panic. Its behavior depends on a couple of conditions in the /rtas node of the device tree, the traversal of which entails locking and local IRQ state changes. If the kernel panics while devtreelock is held, rtasos_term() as currently written could hang.

Instead of discovering the relevant characteristics at panic time, cache them in file-static variables at boot. Note the lookup for "ibm,extended-os-term" is converted to ofpropertyread_bool() since it is a boolean property, not an RTAS function token.

[mpe: Incorporate suggested change from Nick]