The product uses double-checked locking to access a resource without the overhead of explicit synchronization, but the locking is insufficient.
Double-checked locking refers to the situation where a programmer checks to see if a resource has been initialized, grabs a lock, checks again to see if the resource has been initialized, and then performs the initialization if it has not occurred yet. This should not be done, as it is not guaranteed to work in all languages and on all architectures. In summary, other threads may not be operating inside the synchronous block and are not guaranteed to see the operations execute in the same order as they would appear inside the synchronous block.
Threat Mapped score: 1.8
Industry: Finiancial
Threat priority: P4 - Informational (Low)
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| Phase | Note |
|---|---|
| Implementation | N/A |
Intro: It may seem that the following bit of code achieves thread safety while avoiding unnecessary synchronization...
Body: The programmer wants to guarantee that only one Helper() object is ever allocated, but does not want to pay the cost of synchronization every time this code is called.
if (helper == null) { synchronized (this) { if (helper == null) { helper = new Helper(); } } } return helper;