Fenced Memory Slab Guard Buffers for Kernel Corruption Detection
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Solution Overview
Problem
Memory corruption in kernel environments is difficult to debug due to its unpredictable nature and the high memory requirements of existing detection tools, which can lead to program crashes and unexpected behavior, especially in scenarios with limited memory resources.
Innovation Solution
Configuring a memory block as a fenced slab with alternating data and guard buffers, invoking a page fault operation upon attempted write access, and performing a panic routine for invalid addresses while enabling single-step processing for valid addresses to detect and debug memory corruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a debugging tool detects memory corruption at the exact moment of corruption, then detection accuracy is improved, but memory usage increases significantly
Solution Approach 1:
The memory slab is segmented into alternating data buffers and guard buffers. Each guard buffer acts as a sentinel that triggers a page fault when written to, enabling detection of memory corruption without requiring additional monitoring memory. This segmentation allows the system to detect corruption at the exact moment while using minimal extra memory.
Solution Approach 2:
Guard buffers serve as intermediaries between the data buffers and the memory management system. When a buffer overflow occurs, the corruption is directed toward the guard buffer instead of immediately affecting other data, and the guard buffer's write protection mechanism mediates the detection process by triggering a page fault that can be caught and analyzed.
2Measurement precision
If read-only protection is applied to the fenced slab, then memory corruption detection is improved, but write access capability deteriorates
Solution Approach 1:
The read-only protection is applied dynamically rather than statically. The fenced slab is made read-only only when corruption detection is needed, and the protection can be temporarily removed to allow legitimate write operations. This dynamic approach enables the system to switch between protection mode and normal operation mode, resolving the contradiction between detection capability and write access.
Solution Approach 2:
Read-only protection is applied selectively to specific regions (guard buffers) rather than the entire memory slab. The guard buffers have read-only protection to detect overflows, while data buffers maintain normal read-write access. This localized application of protection allows corruption detection without significantly impacting overall write access capability.
3Measurement precision
If guard buffers are inserted between data buffers, then memory corruption detection is improved, but memory overhead increases
Solution Approach 1:
The guard buffers serve multiple functions: they act as sentinels for overflow detection, they trigger page faults when written to, and they provide a mechanism for identifying the location of corruption. By making the guard buffer structure multi-functional, the system achieves comprehensive corruption detection without requiring separate monitoring structures, thereby minimizing memory overhead.
Solution Approach 2:
The system changes the protection parameter (read-only vs. read-write) of the guard buffers to enable detection. When corruption is detected via page fault, the system can modify the protection parameters of the affected slab to allow debugging operations. This parameter change approach enables detection capability while keeping the structural overhead minimal.
Data Source
AI summary
A device identifies, based on a program code instruction, an attempted write access operation to a fenced memory slab, where the fenced memory slab includes an alternating sequence of data buffers and guard buffers. The device assigns read-only protection to the fenced slab and invokes, based on the attempted write access operation, a page fault operation. When a faulting address of the attempted write operation is not an address for one of the multiple data buffers, the device performs a panic routine. When the faulting address of the attempted write operation is an address for one of the multiple data buffers, the device removes the read-only protection for the fenced slab and performs a single step processing routine for the program code instruction.