The product subtracts one pointer from another in order to determine size, but this calculation can be incorrect if the pointers do not exist in the same memory chunk.
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Threat Mapped score: 0.0
Industry: Finiancial
Threat priority: Unclassified
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| Phase | Note |
|---|---|
| Implementation | N/A |
Intro: The following example contains the method size that is used to determine the number of nodes in a linked list. The method is passed a pointer to the head of the linked list.
Body: However, the method creates a pointer that points to the end of the list and uses pointer subtraction to determine the number of nodes in the list by subtracting the tail pointer from the head pointer. There no guarantee that the pointers exist in the same memory area, therefore using pointer subtraction in this way could return incorrect results and allow other unintended behavior. In this example a counter should be used to determine the number of nodes in the list, as shown in the following code.
struct node { int data; struct node* next; }; // Returns the number of nodes in a linked list from // the given pointer to the head of the list. int size(struct node* head) { struct node* current = head; struct node* tail; while (current != NULL) { tail = current; current = current->next; } return tail - head; } // other methods for manipulating the list ...