The application calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().
When free() is called on an invalid pointer, the program's memory management data structures may become corrupted. This corruption can cause the program to crash or, in some circumstances, an attacker may be able to cause free() to operate on controllable memory locations to modify critical program variables or execute code.
cwe_Nature: ChildOf cwe_CWE_ID: 762 cwe_View_ID: 1000 cwe_Ordinal: Primary
cwe_Nature: CanPrecede cwe_CWE_ID: 123 cwe_View_ID: 1000
|['Integrity', 'Confidentiality', 'Availability']||['Execute Unauthorized Code or Commands', 'Modify Memory']||There is the potential for arbitrary code execution with privileges of the vulnerable program via a "write, what where" primitive. If pointers to memory which hold user information are freed, a malicious user will be able to write 4 bytes anywhere in memory.|
Only free pointers that you have called malloc on previously. This is the recommended solution. Keep track of which pointers point at the beginning of valid chunks and free them only once.
Before freeing a pointer, the programmer should make sure that the pointer was previously allocated on the heap and that the memory belongs to the programmer. Freeing an unallocated pointer will cause undefined behavior in the program.
策略: 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.
Use a language that provides abstractions for memory allocation and deallocation.
Use a tool that dynamically detects memory management problems, such as valgrind.
In this example, an array of record_t structs, bar, is allocated automatically on the stack as a local variable and the programmer attempts to call free() on the array. The consequences will vary based on the implementation of free(), but it will not succeed in deallocating the memory.
This example shows the array allocated globally, as part of the data segment of memory and the programmer attempts to call free() on the array.
Instead, if the programmer wanted to dynamically manage the memory, malloc() or calloc() should have been used.
Additionally, you can pass global variables to free() when they are pointers to dynamically allocated memory.
|映射的分类名||ImNode ID||Fit||Mapped Node Name|
|CERT C Secure Coding||MEM34-C||Exact||Only free memory allocated dynamically|
|CERT C Secure Coding||WIN30-C||Imprecise||Properly pair allocation and deallocation functions|
|Software Fault Patterns||SFP12||Faulty Memory Release|