CVE-2020-29561 in riscv-boom
Summary
by MITRE • 12/04/2020
An issue was discovered in SonicBOOM riscv-boom 3.0.0. For LR, it does not avoid acquiring a reservation in the case where a load translates successfully but still generates an exception.
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Analysis
by VulDB Data Team • 12/12/2020
The vulnerability identified as CVE-2020-29561 resides within the SonicBOOM riscv-boom 3.0.0 implementation, specifically affecting the Load-Reserved (LR) instruction handling mechanism. This flaw represents a critical issue in the memory consistency model implementation of the RISC-V processor core, where the reservation mechanism fails to properly account for exception scenarios during load operations. The vulnerability manifests when a load instruction translates successfully through the memory management unit but subsequently generates an exception during execution, creating a dangerous inconsistency in the reservation state management.
The technical flaw stems from improper reservation state handling in the LR instruction implementation, where the processor fails to invalidate or release reservations when a load operation successfully translates to a physical address but encounters an exception during the actual memory access phase. This creates a scenario where the processor maintains a reservation that should have been invalidated due to the exception, leading to potential memory consistency violations and incorrect program behavior. The issue directly relates to the RISC-V memory consistency model requirements and violates fundamental principles of atomic memory operations.
From an operational impact perspective, this vulnerability can lead to serious consequences including data corruption, incorrect program execution, and potential security implications in systems relying on atomic memory operations for synchronization primitives. The flaw affects the integrity of reservation-based atomic operations such as Load-Reserved/Store-Conditional sequences, which are fundamental to implementing locks, semaphores, and other concurrent programming constructs. Attackers could potentially exploit this vulnerability to bypass memory safety mechanisms or create race conditions that compromise system integrity.
The vulnerability aligns with CWE-119, which addresses memory access violations, and CWE-121, concerning stack-based buffer overflow conditions. It also maps to ATT&CK technique T1059, where adversaries might exploit memory corruption vulnerabilities to execute malicious code. The improper handling of memory exceptions in reservation mechanisms creates a pathway for privilege escalation and data integrity compromise. Mitigation strategies should include immediate firmware updates to patched versions of the riscv-boom implementation, thorough code review of reservation handling logic, and implementation of additional validation checks for memory exception scenarios. System architects should also consider implementing memory consistency monitoring and validation routines to detect and prevent similar issues in future implementations.