CodeQL documentation

Not enough memory allocated for array of pointer type

ID: cpp/suspicious-allocation-size
Kind: problem
Severity: warning
Precision: medium
Tags:
   - reliability
   - security
   - external/cwe/cwe-131
   - external/cwe/cwe-122
Query suites:
   - cpp-security-extended.qls
   - cpp-security-and-quality.qls

Click to see the query in the CodeQL repository

When you allocate an array from memory using malloc, calloc or realloc, you should ensure that you allocate enough memory to contain a multiple of the size of the required pointer type. Calls that are assigned to a non-void pointer variable, but do not allocate enough memory will cause a buffer overflow when a field accessed on the pointer points to memory that is beyond the allocated array. Buffer overflows can lead to anything from a segmentation fault to a security vulnerability.

Recommendation

The highlighted call allocates memory that is not a multiple of the size of the pointer type, which can cause a memory overrun. Use the sizeof operator to ensure that the function call allocates enough memory for that type.

Example

#define RECORD_SIZE 30  //incorrect or outdated size for record
typedef struct {
	char name[30];
	int status;
} Record;

void f() {
	Record* p = malloc(RECORD_SIZE * 4); //wrong: not a multiple of the size of Record
	p[3].status = 1; //will most likely segfault
	...
}

References

  • I. Gerg. An Overview and Example of the Buffer-Overflow Exploit. IANewsletter vol 7 no 4. 2005.
  • M. Donaldson. Inside the Buffer Overflow Attack: Mechanism, Method & Prevention. SANS Institute InfoSec Reading Room. 2002.
  • Common Weakness Enumeration: CWE-131.
  • Common Weakness Enumeration: CWE-122.