CVE-2019-18422

An issue was discovered in Xen through 4.12.x allowing ARM guest OS users
to cause a denial of service or gain privileges by leveraging the erroneous
enabling of interrupts. Interrupts are unconditionally unmasked in
exception handlers. When an exception occurs on an ARM system which is
handled without changing processor level, some interrupts are
unconditionally enabled during exception entry. So exceptions which occur
when interrupts are masked will effectively unmask the interrupts. A
malicious guest might contrive to arrange for critical Xen code to run with
interrupts erroneously enabled. This could lead to data corruption, denial
of service, or possibly even privilege escalation. However a precise attack
technique has not been identified.

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