Function returns address of local variable in a global variable

The LOCRET.GLOB checker finds instances in which a function returns the address of a local variable by writing it into a global variable.

Vulnerability and risk

Local variables are allocated on the stack, so when a function returns a pointer to the variable, it's returning a stack address. The address will be invalidated after returning from the function, so access will probably cause unexpected application behavior, typically a program crash.

Vulnerable code example

  #include <stdlib.h>
  int *buf;
  void func_GLOB(unsigned n)
      int aux;
      if (n == 1) {
          buf = &aux;
     } else {
         buf = (int *)malloc(n * sizeof(int));

Klocwork flags line 13 where control leaves function func_GLOB. This indicates that the address of the local variable, aux, which is assigned to a global variable at line 9, is accessible through that global variable after the function returns.

Related checkers

Security training

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