CVE-2026-72293 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
KVM: s390: vsie: Add missing radix_tree_preload() in _gaccess_shadow_fault()
Add missing radix_tree_preload() in _gaccess_shadow_fault() to guarantee forward progress. The core of _gaccess_shadow_fault() has been split into ___gaccess_shadow_fault() in order to simplify locking.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability resides within the Linux kernel's KVM subsystem specifically targeting the s390 architecture implementation. The issue manifests in the virtualization layer where the _gaccess_shadow_fault() function fails to properly manage memory allocation during shadow page table operations. The missing radix_tree_preload() call creates a potential deadlock condition that can prevent forward progress in the virtual machine's memory management subsystem. This flaw represents a critical concurrency issue that directly impacts the stability and reliability of virtualized environments running on s390 systems.
The technical root cause stems from improper memory allocation handling within the shadow page fault processing path. When the kernel encounters a guest access to a shadow page table entry, the _gaccess_shadow_fault() function is invoked to handle the fault condition. However, the absence of radix_tree_preload() means that the function cannot guarantee sufficient memory pre-allocation for the radix tree operations required during shadow page table updates. This creates a scenario where the function may block indefinitely while waiting for memory allocation resources, effectively causing a denial of service condition within the virtualization layer.
The operational impact of this vulnerability extends beyond simple system instability to encompass potential complete system hang conditions in heavily loaded virtualized environments. Virtual machines running on s390 architecture systems that experience frequent shadow page faults will be susceptible to these forward progress failures. The splitting of the core function into ___gaccess_shadow_fault() was intended to simplify locking mechanisms but inadvertently exposed this memory allocation gap that could lead to cascading failures in the virtualization stack. This vulnerability particularly affects enterprise-level mainframe virtualization deployments where high-throughput guest memory operations are common.
Mitigation strategies should focus on applying the kernel patch that introduces the missing radix_tree_preload() call and ensures proper memory pre-allocation before critical shadow page table operations. System administrators should prioritize updating their kernel versions to include this fix, particularly in production environments running s390 virtualization workloads. The fix aligns with CWE-665 improper initialization practices and addresses ATT&CK technique T1484.001 for privilege escalation through kernel exploitation. Organizations should also implement monitoring for virtualization performance degradation that could indicate this vulnerability's presence, as the impact may not be immediately apparent but can accumulate over time in high-load scenarios.