CWE-590 释放并不在堆上的内存

Free of Memory not on the Heap

结构: Simple

Abstraction: Variant

状态: Incomplete

被利用可能性: unkown

基本描述

The application calls free() on a pointer to memory that was not allocated using associated heap allocation functions such as malloc(), calloc(), or realloc().

扩展描述

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.

相关缺陷

  • 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

常见的影响

范围 影响 注释
['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.

可能的缓解方案

Implementation

策略:

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.

Implementation

策略:

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.

MIT-4.6 Architecture and Design

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.

Architecture and Design

策略:

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

Testing

策略:

Use a tool that dynamically detects memory management problems, such as valgrind.

示例代码

例

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.

bad C

void foo(){
record_t bar[MAX_SIZE];

/ do something interesting with bar /

...
free(bar);
}

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.

bad C

record_t bar[MAX_SIZE]; //Global var
void foo(){

/ do something interesting with bar /
...
free(bar);
}

Instead, if the programmer wanted to dynamically manage the memory, malloc() or calloc() should have been used.

good

void foo(){
record_t bar = (record_t)malloc(MAX_SIZEsizeof(record_t));

/ do something interesting with bar */

...
free(bar);
}

Additionally, you can pass global variables to free() when they are pointers to dynamically allocated memory.

good

record_t bar; //Global var
void foo(){
bar = (record_t)malloc(MAX_SIZEsizeof(record_t));

/ do something interesting with bar */

...
free(bar);
}

Notes

分类映射

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

引用