The result of calling malloc(0), or calling calloc() to allocate 0 bytes (calloc(1,0), calloc(0,0), or calloc(0,1)) is undefined. From a practical standpoint, allocating 0 bytes with calloc() and malloc() can lead to programming errors with critical security implications, such as buffer overflows. This occurs because the result of allocating 0 bytes with calloc() and malloc() may not considered an error, thus the pointer returned may not be NULL. Instead, the pointer may reference a block of memory on the heap of size zero. If memory is fetched from, or stored in this a location serious error could occur. Numerous, vulnerabilities may allow the allocation of 0 bytes with calloc and malloc, such as VU#179014, VU#226184, and VU#855118.
Non-compliant Code Example 1
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| Code Block |
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size_t str_size = calc_size(other_string);
if (str_size > 0) {
char *str_copy = malloc(str_size);
if (str_copy == NULL) {
/* handle error */
}
strcpy(str_copy, other_string);
}
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References
- Seacord 05 Chapter 4 Dynamic Memory Management