Generation of Error Message Containing Sensitive Information

Summary

In x86's APIC (Advanced Programmable Interrupt Controller) architecture, error conditions are reported in a status register. Furthermore, the OS can opt to receive an interrupt when a new error occurs. It is possible to configure the error interrupt with an illegal vector, which generates an error when an error interrupt is raised. This scenario causes Xen to recurse through "vlapic_error()". The recursion itself is bounded; errors accumulate in the status register and only generate an interrupt when a new status bit becomes set. However, the lock protecting this state in Xen will attempt to be taken recursively, causing a deadlock. The vulnerability affects 4.5.0-rc1 through 4.16.6, 4.17.0-rc1 through 4.18.4, and 4.19.0-rc1 through 4.19.0, and 4.20-dev.