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Description
The software unlocks a critical resource more times than intended, leading to an unexpected state in the system.
When software is operating in a concurrent environment and repeatedly unlocks 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 calls to unlock will increase the count for the number of available resources, likely resulting in a crash or unpredictable behavior when the system nears capacity.
Modes of Introduction:
– Implementation
Likelihood of Exploit:
Related Weaknesses
CWE-667
CWE-675
Consequences
Availability, Integrity: DoS: Crash, Exit, or Restart, Modify Memory, Unexpected State
Potential Mitigations
Phase: Implementation
Effectiveness:
Description:
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.
CVE References
- CVE-2009-0935
- Attacker provides invalid address to a memory-reading function, causing a mutex to be unlocked twice
