Common Weakness Enumeration

A Community-Developed List of Software Weakness Types

CWE/SANS Top 25 Most Dangerous Software Errors
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CWE-764: Multiple Locks of a Critical Resource

Weakness ID: 764
Abstraction: Variant
Status: Incomplete
Presentation Filter:
+ Description

Description Summary

The software locks a critical resource more times than intended, leading to an unexpected state in the system.

Extended Description

When software is operating in a concurrent environment and repeatedly locks a critical resource, the consequences will vary based on the type of lock, the lock's implementation, and the resource being protected. In some situations such as with semaphores, the resources are pooled and extra locking calls will reduce the size of the total available pool, possibly leading to degraded performance or a denial of service. If this can be triggered by an attacker, it will be similar to an unrestricted lock (CWE-412). In the context of a binary lock, it is likely that any duplicate locking attempts will never succeed since the lock is already held and progress may not be possible.

+ Time of Introduction
  • Architecture and Design
  • Implementation
+ Common Consequences

Technical Impact: DoS: resource consumption (CPU); DoS: crash / exit / restart; Unexpected state

+ Potential Mitigations

Phase: Implementation

When locking and unlocking a resource, try to be sure that all control paths through the code in which the resource is locked one or more times correspond to exactly as many unlocks. If the software acquires a lock and then determines it is not able to perform its intended behavior, be sure to release the lock(s) before waiting for conditions to improve. Reacquire the lock(s) before trying again.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness BaseWeakness Base667Improper Locking
Development Concepts (primary)699
Research Concepts (primary)1000
ChildOfWeakness ClassWeakness Class675Duplicate Operations on Resource
Research Concepts1000
ChildOfCategoryCategory987SFP Secondary Cluster: Multiple Locks/Unlocks
Software Fault Pattern (SFP) Clusters (primary)888
+ Taxonomy Mappings
Mapped Taxonomy NameNode IDFitMapped Node Name
Software Fault PatternsSFP21Multiple locks/unlocks
+ Maintenance Notes

An alternate way to think about this weakness is as an imbalance between the number of locks / unlocks in the control flow. Over the course of execution, if each lock call is not followed by a subsequent call to unlock in a reasonable amount of time, then system performance may be degraded or at least operating at less than peak levels if there is competition for the locks. This entry may need to be modified to reflect these concepts in the future.

+ Content History
Submission DateSubmitterOrganizationSource
2009-03-03Internal CWE Team
Modification DateModifierOrganizationSource
2011-06-01CWE Content TeamMITREInternal
updated Common_Consequences
2011-06-27CWE Content TeamMITREInternal
updated Common_Consequences
2012-05-11CWE Content TeamMITREInternal
updated Relationships
2014-07-30CWE Content TeamMITREInternal
updated Relationships, Taxonomy_Mappings

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Page Last Updated: May 05, 2017