CVE-2007-3107 in Linux
Summary
by MITRE
The signal handling in the Linux kernel before 2.6.22, including 2.6.2, when running on PowerPC systems using HTX, allows local users to cause a denial of service via unspecified vectors involving floating point corruption and concurrency, related to clearing of MSR bits.
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Analysis
by VulDB Data Team • 07/22/2019
The vulnerability described in CVE-2007-3107 represents a critical flaw in the Linux kernel's signal handling mechanism on PowerPC systems utilizing HTX technology. This issue affects kernel versions prior to 2.6.22, including the widely used 2.6.2 release, creating a significant security risk for systems running on PowerPC architecture. The vulnerability specifically targets the interaction between signal processing and hardware state management during concurrent execution scenarios.
The technical root cause of this vulnerability lies in the improper handling of Machine State Register (MSR) bits during signal delivery on PowerPC systems. When signals are processed in the kernel context, the system fails to correctly manage the MSR state, particularly when dealing with floating point operations and concurrent access patterns. This flaw manifests when the kernel attempts to clear specific MSR bits during signal handling routines, leading to unpredictable behavior that can result in system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it fundamentally compromises the reliability of signal handling mechanisms on affected PowerPC systems. Local attackers can exploit this weakness to trigger system crashes or lockups through carefully crafted sequences that leverage the floating point corruption and concurrency issues. The vulnerability is particularly dangerous in multi-threaded environments where multiple processes or threads may be simultaneously processing signals, creating race conditions that amplify the potential for system failure.
This vulnerability aligns with CWE-119, which addresses improper restriction of operations within a memory buffer, and demonstrates the intersection of hardware state management with software signal handling. The attack vector involves leveraging the kernel's signal delivery mechanism to manipulate processor state registers, which falls under the ATT&CK technique T1499.004 for Network Denial of Service. The flaw essentially creates a condition where the kernel's signal handling code path becomes unstable when dealing with concurrent access patterns involving floating point operations, making it a prime candidate for exploitation in environments where multiple processes are actively using floating point units.
Mitigation strategies for this vulnerability require immediate kernel updates to versions 2.6.22 or later, where the signal handling code has been restructured to properly manage MSR bits during signal delivery. System administrators should also implement monitoring solutions to detect unusual signal processing patterns that might indicate exploitation attempts. Additionally, organizations should consider implementing runtime protections that can detect and prevent the specific MSR bit manipulation patterns associated with this vulnerability, particularly in mission-critical systems where availability is paramount. The fix implemented in the kernel addresses the core issue by ensuring proper synchronization and state management during signal processing, eliminating the race conditions that previously led to MSR bit corruption.