Take the SRCU lock for page table walks in fault injection and AT emulation

Summary

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation walk_s1() and kvm_walk_nested_s2() expect to be called while holding kvm->srcu to guard against memslot changes. While this is generally the case, __kvm_at_s12() and __kvm_find_s1_desc_level() call into the respective walkers without taking kvm->srcu. Fix by acquiring kvm->srcu prior to the table walk in both instances. A flaw was found in the Kernel-based Virtual Machine (KVM) component of the Linux kernel on arm64 architectures. This vulnerability occurs because certain page table walk operations, used in fault injection and Address Translation (AT) emulation, do not properly acquire a Sleepable Read-Copy Update (SRCU) lock. This omission could lead to inconsistencies in memory slot management, potentially causing system instability or unexpected behavior within the virtualized environment. Red Hat severity: Important — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-820. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.