Improper Resource Locking
The software does not lock or does not correctly lock a resource when the software must have exclusive access to the resource.
When a resource is not properly locked, an attacker could modify the resource while it is being operated on by the software. This might violate the software's assumption that the resource will not change, potentially leading to unexpected behaviors.
The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.
Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.
The following function attempts to acquire a lock in order to perform operations on a shared resource.
However, the code does not check the value returned by pthread_mutex_lock() for errors. If pthread_mutex_lock() cannot acquire the mutex for any reason the function may introduce a race condition into the program and result in undefined behavior.
In order to avoid data races correctly written programs must check the result of thread synchronization functions and appropriately handle all errors, either by attempting to recover from them or reporting it to higher levels.
This Java example shows a simple BankAccount class with deposit and withdraw methods.
However, the deposit and withdraw methods have shared access to the account balance private class variable. This can result in a race condition if multiple threads attempt to call the deposit and withdraw methods simultaneously where the account balance is modified by one thread before another thread has completed modifying the account balance. For example, if a thread attempts to withdraw funds using the withdraw method before another thread that is depositing funds using the deposit method completes the deposit then there may not be sufficient funds for the withdraw transaction.
To prevent multiple threads from having simultaneous access to the account balance variable the deposit and withdraw methods should be synchronized using the synchronized modifier.
An alternative solution is to use a lock object to ensure exclusive access to the bank account balance variable. As shown below, the deposit and withdraw methods use the lock object to set a lock to block access to the BankAccount object from other threads until the method has completed updating the bank account balance variable.
Weaknesses in this category are related to the rules and recommendations in the Visibility and Atomicity (VNA) section of the SEI CERT Oracle Secure Coding Standard fo...
This category identifies Software Fault Patterns (SFPs) within the Missing Lock cluster (SFP19).
Weaknesses in this category are related to improper handling of locks that are used to control access to resources.
This view (slice) covers all the elements in CWE.
This view (slice) lists weaknesses that can be introduced during implementation.
This view (slice) lists weaknesses that can be introduced during design.