SPP: Safe Persistent Pointers for Memory Safety

Memory safety violations, such as buffer overflows, are the primary cause of security and reliability issues in software systems. Like the volatile main memory, byte-addressable persistent memory (PM) storage devices are also prone to memory safety exploits because PM devices are directly mapped to the address space and accessed via the load/store interface using pointers. However, the PM pointer representation is persistent, i.e., its offset and the associated object are persistent across system reboots. Therefore, the current memory safety mechanisms for the volatile main memory are inadequate for ensuring the safety of persistent pointers. To this end, we propose Safe Persistent Pointers (SPP), a practical memory safety approach against buffer overflows for PM applications. SPP augments persistent pointers with memory safety properties. SPP is based on a simple combination of tagged pointers, efficient persistent memory layout, and transactional updates to the memory safety metadata for ensuring crash consistency. SPP's efficient pointer representation does not require additional memory lookup operations at runtime while incurring minimal space overheads for storing the memory safety metadata. We implement SPP based on the LLVM compiler infrastructure accompanied by a runtime library and an adapted version of PM development kit (PMDK). Our evaluation demonstrates that SPP incurs low runtime and space overheads while preserving the crash-consistency property and maintaining the PMDK API intact, i.e., requiring no source code modifications.