Rogue code can take down Linux systems

• Tags:
• Attack,
• Code,
• Linux,
• Flaw

Published: 16 Jun 2004 08:55 BST

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Linux users have been urged to fix a flaw in the core component of the open-source operating system, following the public release of code that could be used to crash Linux systems.

The flaw, found by two software programmers, could give a user with access to a Linux system the ability to crash the system using two dozen lines of code written in the C programming language, said an advisory posted over the weekend on linuxreviews.

"Assume your kernel is (vulnerable) unless you have good reason to believe it is safe," Oyvind Saether, one of the discoverers of the flaw, said in the advisory.

The program, dubbed "evil.c," causes problems with the code sent to the floating-point unit, the part of the processor that handles noninteger calculations, according to a note in a source code patch published by Linux founder Linus Torvalds.

The open-source Linux operating system has fallen prey to its share of flaws and attacks this year. Several flaws were found in the Concurrent Versions System, CVS, a commonly used application for managing open-source code under development. In March and April, online attackers targeted Linux and Solaris systems at many academic high-performance computing centres.

Researchers also found flaws in the OpenSSL software used by many Linux distributions to enable secure Internet communications.

On Monday, staffers associated with Red Hat's community-based distribution, Fedora, released an update to Fedora Core 2, to fix the latest problem. The kernel patch has also been included in the latest release candidate of the Linux kernel, 2.6.7-RC3, which is expected to be released soon.

Other distributions of Linux should be fixed this week as well.

Andrew Morton, the maintainer of the Linux 2.6 kernel, promised a fix within 48 hours and said the flaw was not very serious.

"Bugs wherein local users can lock the machine up are not uncommon, and local users have always been able to bring a machine to its knees anyway -- say, by using up all the memory," he said.

Morton said the discoverers of the flaw didn't give the kernel team any notice before releasing the code to take advantage of the problem -- a no-no in the security community.

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