CVE-2005-3356 in Linux
Summary
by MITRE
The mq_open system call in Linux kernel 2.6.9, in certain situations, can decrement a counter twice ("double decrement") as a result of multiple calls to the mntput function when the dentry_open function call fails, which allows local users to cause a denial of service (panic) via unspecified attack vectors.
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Analysis
by VulDB Data Team • 07/07/2021
The vulnerability identified as CVE-2005-3356 represents a critical race condition and memory management flaw within the Linux kernel's message queue implementation. This issue manifests specifically in kernel versions up to 2.6.9 where the mq_open system call exhibits improper reference counting behavior under certain failure conditions. The flaw occurs when the dentry_open function encounters an error during execution, leading to a cascade of function calls that ultimately results in the decrementing of a reference counter twice. This double decrement operation creates a scenario where kernel memory structures become corrupted or improperly managed, leading to system instability.
The technical implementation of this vulnerability stems from the interaction between multiple kernel subsystems including the filesystem layer and the message queue subsystem. When a process attempts to open a message queue through the mq_open system call, the kernel performs various checks and operations including dentry_open function calls to validate the target filesystem entry. Under failure conditions, the mntput function gets invoked multiple times in sequence, each invocation attempting to decrement the same reference counter. This improper handling violates fundamental kernel memory management principles where reference counters should only be decremented once per corresponding increment operation. The vulnerability is classified under CWE-129 as an improper input validation, specifically related to incorrect reference counting mechanisms that can lead to memory corruption.
From an operational perspective, this vulnerability presents a significant denial of service risk that can be exploited by local users to crash the entire system. The panic condition triggered by the double decrement results in a kernel oops or system crash, effectively rendering the affected system unavailable to legitimate users. The attack vectors remain unspecified in the original CVE description, indicating that multiple pathways could lead to triggering this condition, making the vulnerability particularly concerning for system administrators. The impact extends beyond simple service disruption as the kernel panic can potentially lead to data loss or corruption if the system is in the middle of critical operations. This vulnerability aligns with ATT&CK technique T1499.004 which involves network disruption through system resource exhaustion or corruption, although in this case the disruption occurs through kernel memory corruption rather than network-based attacks.
The mitigation strategies for CVE-2005-3356 primarily involve upgrading to kernel versions where this issue has been resolved, typically kernel versions 2.6.10 and later. System administrators should prioritize patching affected systems as this vulnerability represents a fundamental kernel flaw that can be exploited by any local user with access to the system. Additionally, monitoring for unusual system crashes or kernel oops messages can help detect exploitation attempts. The fix implemented in subsequent kernel versions typically involves proper synchronization mechanisms and ensuring that reference counting operations occur only once per valid operation, preventing the double decrement scenario from occurring. Organizations should also implement proper kernel version management policies to ensure all systems are running patched versions and maintain regular security updates to prevent similar vulnerabilities from being exploited.