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Many library functions take pointers as arguments. If the pointer passed to a library function does not refer to valid memory, the results are [undefined|BB. Definitions#undefined] (see [EXP34-C. Ensure a null pointer is not dereferenced]). Typically the program will terminate abnormally when the invalid pointer is dereferenced, but it is possible, and quite common, for an invalid pointer to be dereferenced, and its memory changed, without abnormal termination \[[Jack 07|AA. C References#Jack 07]\]. Such programs can be very difficult to debug due to the difficulty of determining the pointer's lack of validity. |
One source of prevention of invalid pointers would be a function that could take a pointer and indicate if the pointer is 'valid' or not, for some definition of valid. For instance, here is a function that declares any pointer to be valid except NULL.
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Search for vulnerabilities resulting from the violation of this rule on the CERT website.
References
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\[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\] Section 6.3.2.3, "Pointers"
\[[Jack 07|AA. C References#Jack 07]\]
\[[van Sprundel 06|AA. C References#van Sprundel 06]\] |
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MEM09-A. Do not assume memory allocation routines initialize memory 08. Memory Management (MEM)