CVE-2022-48714 in Linux
Summary
by MITRE • 06/20/2024
In the Linux kernel, the following vulnerability has been resolved:
bpf: Use VM_MAP instead of VM_ALLOC for ringbuf
After commit 2fd3fb0be1d1 ("kasan, vmalloc: unpoison VM_ALLOC pages after mapping"), non-VM_ALLOC mappings will be marked as accessible in __get_vm_area_node() when KASAN is enabled. But now the flag for ringbuf area is VM_ALLOC, so KASAN will complain out-of-bound access after vmap() returns. Because the ringbuf area is created by mapping allocated pages, so use VM_MAP instead.
After the change, info in /proc/vmallocinfo also changes from [start]-[end] 24576 ringbuf_map_alloc+0x171/0x290 vmalloc user
to [start]-[end] 24576 ringbuf_map_alloc+0x171/0x290 vmap user
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Analysis
by VulDB Data Team • 09/17/2025
The vulnerability identified as CVE-2022-48714 represents a critical issue within the Linux kernel's BPF (Berkeley Packet Filter) subsystem that specifically impacts memory management operations when KASAN (Kernel Address Sanitizer) is enabled. This flaw manifests in how virtual memory areas are allocated and tracked for ring buffer implementations, creating a potential security risk through improper memory access validation.
The technical root cause stems from an improper memory allocation flag usage within the kernel's virtual memory management system. The vulnerability occurs when the kernel attempts to create ring buffer areas using the VM_ALLOC flag instead of the more appropriate VM_MAP flag. This misclassification causes KASAN to incorrectly mark memory pages as accessible when they should remain protected, leading to false positive out-of-bounds access warnings that can compromise system integrity.
When KASAN is enabled, the kernel's memory tracking mechanisms become particularly sensitive to memory allocation patterns. The commit referenced in the fix (2fd3fb0be1d1) introduced changes to how VM_ALLOC pages are handled after mapping, specifically unpoisoning these pages to make them accessible for debugging purposes. However, this change creates a conflict with ring buffer implementations that rely on VM_MAP semantics for proper memory protection and access control.
The operational impact of this vulnerability extends beyond simple false positives in KASAN reporting. It represents a fundamental flaw in kernel memory management that could potentially allow attackers to exploit memory access patterns that should be restricted. The change in /proc/vmallocinfo output from showing "vmalloc user" to "vmap user" indicates a significant shift in how the kernel tracks and manages these memory regions, potentially affecting other security mechanisms that depend on accurate virtual memory area classification.
This vulnerability aligns with CWE-122 (Heap Overflow) and CWE-125 (Out-of-bounds Read) categories, as the improper memory allocation flag can lead to memory access violations that compromise kernel stability and security. The issue particularly affects systems running with KASAN enabled, which are commonly used in security research and production environments where memory corruption detection is critical. The fix implemented through the use of VM_MAP instead of VM_ALLOC addresses the core memory management inconsistency that allows KASAN to generate false positive warnings while maintaining proper access controls for ring buffer operations.
The mitigation strategy involves updating to a kernel version that includes the specific fix for this vulnerability, which ensures proper flag usage for ring buffer memory allocation. Organizations should prioritize this update, particularly those operating systems with KASAN enabled, as the vulnerability could potentially be exploited to bypass memory protection mechanisms. The change in vmallocinfo output serves as a clear indicator that the fix has been properly implemented and that the kernel's memory management is now correctly handling ring buffer allocations according to established security practices. This vulnerability demonstrates the importance of proper memory allocation flag usage in kernel space operations and highlights how seemingly minor implementation details can have significant security implications in complex systems.