Deletion of Data Structure Sentinel

The accidental deletion of a data-structure sentinel can cause serious programming logic problems.


Description

Often times data-structure sentinels are used to mark structure of the data structure. A common example of this is the null character at the end of strings. Another common example is linked lists which may contain a sentinel to mark the end of the list. It is dangerous to allow this type of control data to be easily accessible. Therefore, it is important to protect from the deletion or modification outside of some wrapper interface which provides safety.

Demonstrations

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.

Example One

This example creates a null terminated string and prints it contents.

char *foo;
int counter;
foo=calloc(sizeof(char)*10);

for (counter=0;counter!=10;counter++) {
  foo[counter]='a';

printf("%s\n",foo);
}

The string foo has space for 9 characters and a null terminator, but 10 characters are written to it. As a result, the string foo is not null terminated and calling printf() on it will have unpredictable and possibly dangerous results.

See Also

SFP Secondary Cluster: Design

This category identifies Software Fault Patterns (SFPs) within the Design cluster.

Data Neutralization Issues

Weaknesses in this category are related to the creation or neutralization of data using an incorrect format.

Comprehensive CWE Dictionary

This view (slice) covers all the elements in CWE.

Weaknesses without Software Fault Patterns

CWE identifiers in this view are weaknesses that do not have associated Software Fault Patterns (SFPs), as covered by the CWE-888 view. As such, they represent gaps in...

Weaknesses Introduced During Implementation

This view (slice) lists weaknesses that can be introduced during implementation.


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