Book Image

Linux System Programming Techniques

By : Jack-Benny Persson
5 (1)
Book Image

Linux System Programming Techniques

5 (1)
By: Jack-Benny Persson

Overview of this book

Linux is the world's most popular open source operating system (OS). Linux System Programming Techniques will enable you to extend the Linux OS with your own system programs and communicate with other programs on the system. The book begins by exploring the Linux filesystem, its basic commands, built-in manual pages, the GNU compiler collection (GCC), and Linux system calls. You'll then discover how to handle errors in your programs and will learn to catch errors and print relevant information about them. The book takes you through multiple recipes on how to read and write files on the system, using both streams and file descriptors. As you advance, you'll delve into forking, creating zombie processes, and daemons, along with recipes on how to handle daemons using systemd. After this, you'll find out how to create shared libraries and start exploring different types of interprocess communication (IPC). In the later chapters, recipes on how to write programs using POSIX threads and how to debug your programs using the GNU debugger (GDB) and Valgrind will also be covered. By the end of this Linux book, you will be able to develop your own system programs for Linux, including daemons, tools, clients, and filters.
Table of Contents (14 chapters)

Finding buffer overflows with Valgrind

Valgrind can also help us find buffer overflows. That is when we put more data in a buffer than it can hold. Buffer overflows are the cause of many security bugs and are hard to detect. But with Valgrind, it gets a little easier. It might not be 100% accurate at all times, but it's a really good help along the way.

Knowing how to find buffer overflows will make your program more secure.

Getting ready

For this recipe, you'll need the GCC compiler, the Make tool, and the Makefile from the Starting GDB recipe in this chapter.

How to do it…

In this recipe, we'll write a small program that copies too much data into a buffer. We'll then run the program through Valgrind and see how it points out the problem:

  1. Write the following code in a file and save it as overflow.c. The program allocates 20 bytes with calloc(), then copies a string of 26 bytes into that buffer. It then frees up the memory using free...