From the Linux kernel vulnerability perspective system security

Compared with Windows, Linux is considered to have better security, and other extensibility.

These characteristics make the front runner in the field of the operating system Linux, get more and more attention. As the Linux application volume increased its security, or slowly by the public or even hackers. So, Linux really as it supports manufacturers who claims to be as secure as? Linux kernel shorter, high stability, scalability and hardware requirements is low, free, network feature-rich, suitable for a wide variety of cpu features, areas of the operating system. Its unique charm make it not only on PC occupy a certain share, but also increasingly being used in a variety of embedded devices, and is treated as a professional routers, firewalls, or high-end server OS to use. Various types of Linux distributions also sprang up, is sparking a wave of Linux use, many government departments are also required for security requires the use of the Linux-Linux is precisely because of the increasing use of security and has gradually been public concern, of course, but also more attention by the hackers. Typically, we discuss the Linux system security from the point of view of Linux security configuration or Linux security features, to discuss, and this time we convert the angle of view, from the Linux system vulnerability and the impact of these vulnerabilities to discuss Linux security. First of all to explain this time we discussed the scope of Linux system security, but usually we say Linux is the GNU/Linux system, Linux is the operating system used in the system kernel. This time our focus from Linux system kernel in class very characteristics of vulnerability to discuss Linux system's security. Privilege escalation vulnerability in General, the use of such systems on some program logic flaws or buffer overflow means that an attacker can easily obtain the local Linux server administrator permissions for the remote root; in some circumstances, an attacker could use some as root to perform the defective system daemon to obtain root privileges, or the use of defective services process to obtain a normal user to the permissions for remote logging server. There are many Linux servers are used to close all unnecessary services and processes to enhance their own security, but as long as the server running a certain service, the attacker can find privilege escalation. The following is a relatively new lead to privilege elevation vulnerability. Do_brk () border checks does not fully exploit the month of September 2003, is the Linux kernel developers discover and publish by the end of September in Linuxkernel2.6.0-test6 patched. But the Linux kernel developers are not aware of this vulnerability, so didn't do any bulletin, some security experts and hackers but saw this vulnerability implication of power. In November 2003, one of the hackers use rsync does not expose a heap overflow and this vulnerability, and successfully attacked more than one Debian server with GentooLinux. Let's briefly describe the vulnerability. This vulnerability was discovered in brk system call. Brk system call to the user process and the size of the heap, the heap expansion or shrink. And brk internal is directly using do_brk () function to do a specific action, do_brk () function to adjust the process heap is neither on the parameter len any check (do not check the size nor examine the positive and negative), nor whether the addr + len exceeds TASK_SIZE do check. So that we can be submitted to it by the len parameter of any size, the size of the user process as well as any change may exceed the limit, making TASK_SIZE system that kernel scope memory space can be accessed by the user, so normal users can access to the kernel's memory area. Through certain operations, the attacker can gain administrator privileges. This vulnerability is extremely dangerous, the use of this vulnerability may allow an attacker to regional operations to the kernel directly, you can bypass many Linux system security module. The discovery of this vulnerability introduced a new concept of vulnerability by extended user memory space to the system kernel memory space to escalate privileges. When you discover this kind of vulnerability, through research, we believe that the kernel must also be a similar vulnerability, sure enough, a few months after the hackers in the Linux kernel discovered and brk similar vulnerability. Through this successful prediction, confirmed on this new type of vulnerability research is gainianxing help security staff in the system to discover new vulnerabilities. Denial of service vulnerability to denial of service attacks is currently more popular attacks, it does not have server access, but to make the server crashes or freezes. Denial of service on Linux, most of which are not logged on to system a denial of service attack, so that the system or the relevant application crashes or freezes ability, which belongs to the use of the system itself vulnerability or its daemon defects and incorrect settings. The other case, an attacker to login to Linux systems, the use of this type of vulnerability, or you can make the system itself or the application to crash. This vulnerability is mainly composed of procedures for the handling of unexpected situations, such as caused by mistakes in writing temporary files before does not check whether the file exists, blindly follow links, etc. Below, we briefly describe the Linux in handling intelIA386CPU error occurred in the registers of denial of service vulnerability. This vulnerability is due to the use of multimedia instruction IA386 register MXcsR features. As a result of the provisions of the MXCSR registers IA386CPU high 16-bit cannot have any bit is set, otherwise the CPU would be an error causes the system to crash. In order to guarantee the normal operation of the system, in a Linux system is a piece of codeSpecialized on the characteristics of the MXCSR, and this piece of code in a particular case an error occurs,