Free of Pointer not at Start of Buffer

Opis

The product calls free() on a pointer to a memory resource that was allocated on the heap, but the pointer is not at the start of the buffer.

This can cause the product to crash, or in some cases, modify critical program variables or execute code.

This weakness often occurs when the memory is allocated explicitly on the heap with one of the malloc() family functions and free() is called, but pointer arithmetic has caused the pointer to be in the interior or end of the buffer.

Skutki

• Integrity, Availability, Confidentiality

  Modify Memory; DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands

Zapobieganie

• Implementation

  When utilizing pointer arithmetic to traverse a buffer, use a separate variable to track progress through memory and preserve the originally allocated address for later freeing.

• Implementation

  When programming in C++, consider using smart pointers provided by the boost library to help correctly and consistently manage memory.

• Architecture and Design · Libraries or Frameworks

  Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

  For example, glibc in Linux provides protection against free of invalid pointers.

• Architecture and Design

  Use a language that provides abstractions for memory allocation and deallocation.

Przykłady podatności

• CVE-2019-11930 function "internally calls 'calloc' and returns a pointer at an index... inside the allocated buffer. This led to freeing invalid memory."

Słabość nadrzędna

• CWE-763 Release of Invalid Pointer or Reference
• CWE-404 Improper Resource Shutdown or Release

Kiedy powstaje

• Implementation

Dotyczy

Memory-Unsafe, C

Uwagi

Currently, CWE-763 is the parent, however it may be desirable to have an intermediate parent which is not function-specific, similar to how CWE-762 is an intermediate parent between CWE-763 and CWE-590.

Źródła

1. boost C++ Library Smart Pointers
2. Valgrind
3. AddressSanitizer