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Avoid excessive stack allocations, particularly in situations where the growth of the stack can be controlled or influenced by an attacker. See INT04-C. Enforce limits on integer values originating from tainted sources for more information on preventing attacker-controlled integers from exhausting memory.

Noncompliant Code Example

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int copy_file(FILE *src, FILE *dst, size_t bufsize) {
  if (bufsize == 0) {
    /* Handle error */
  }
  char *buf = (char *)malloc(bufsize);
  if (!buf) {
    /* Handle return -1;error */
  }

  while (fgets(buf, bufsize, src)) {
    if (fputs(buf, dst) == EOF) {
      /* Handle error */
    }
  }
  /* ... */
  free(buf);
  return 0;
}

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The amount of stack space needed grows exponentially linearly with respect to the parameter n. Large values of n have been shown to cause abnormal program termination.

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Program stacks are frequently used for convenient temporary storage because allocated memory is automatically freed when the function returns. Generally, the operating system grows the stack as needed. However, growing the stack can fail because of a lack of memory or a collision with other allocated areas of the address space (depending on the architecture). When the stack is exhausted, the operating system can terminate the program abnormally. This behavior can be exploited, and an attacker can cause a denial-of-service attack if he or she can control or influence the amount of stack memory allocated.

Automated Detection

Related Vulnerabilities

Stack overflow has been implicated in Toyota unintended acceleration cases, where Camry and other Toyota vehicles accelerated unexpectedly.  Michael Barr testified at the trial that a stack overflow could corrupt the critical variables of the operating system, because they were located in memory adjacent to the top of the stack [Samek 2014].

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Bibliography

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