Torvalds’ Bug Warning is a Lesson for Linux Users

Linux does, occasionally, raise security concerns. While many users see it as the most secure, robust and versatile operating system available — that’s this writer’s opinion, as well — security precautions still have to be taken.

A recent, widely publicized case illustrated this point; Linux creator himself, Linus Torvalds, warned against the use of the Linux 5.12 release. He described a “nasty bug,” and wrote that the situation is a “mess,” due to the use of swap files when adding Linux updates. This nasty bug, in fact, had the potential to destroy entire root directories.

Some of the main takeaways following this “mess” include: tread very carefully when installing early Linux releases, especially those that involve swapping files instead of partitions, and especially, despite Linux’s well-known security advantages, avoid becoming complacent, because Linux security is not always foolproof.

Hence, while the “state of Linux security today is quite good, and has evolved in a positive way with more visibility and security features built, like many operating systems, you must install, configure and manage it with security in mind; that is how cybercriminals take advantage, [via] the human touch,” said Joseph Carson, chief security scientist and advisory CISO at Thycotic, a provider of privileged access management (PAM) solutions.

A Patch for Nastiness

As Torvalds noted a few weeks ago, “most people don’t use a swap file, but a separate swap partition and the bug in question really only happens when you have a regular file system, and put a file on as a swap.”

“The bad news is that the reason we support swap files in the first place is that they do end up having some flexibility advantages, and so some people do use them for that reason. If so, do not use [release candidate] RC1,” Torvalds wrote. “Thus, the renaming of the tag.”

After issuing the warning, Torvalds released a patch that he says prevents the bug from destroying swap file systems. However, it may have already been too late for early adopters of release 5.12. Ubuntu, a leading Linux distro, can swap files by default.

“It is nasty bug if you are still using swap files,” Carson said. “If you do still use swap files, then you could be impacted, resulting in potential data loss or a corrupted system.”

DevOps teams – or anyone else running Linux and installing patches, whether on multi-servers or on individual workstations – still need, of course, to follow strict best practices. “Like any operating system, security depends entirely on how you use, configure or manage the operating system,” Carson said. “Each new Linux update tries to improve security; however, to get the value, you must enable and configure it correctly.”

Linux Goodness

The fact that Torvalds was so forthcoming about the bug, as well as the level of transparency that the Linux kernel offers, also demonstrates one of the many reasons Linux remains popular. Given that the Linux kernel, in one variety or another, is used “not only in about 50% of the internet servers of the world, but also in a substantial part of all our smartphones, it is good to see this level of transparency at ‘root level,” said Dirk Schrader, global vice president, security research at New Net Technologies (NNT), which providers cybersecurity and compliance software.

“The security of Linux is based on its transparency; the ability to review the code of a distribution,” says Schrader. “Quite often forgotten is that transparency also involves talking about the mistakes, the errors, those nasty bugs.”

Citing National Institute of Standards and Technology (NIST) vulnerability database statistics, Schrader described how, compared to the Windows family of desktop and server operating systems, for example, the Linux kernel shows better results for overall vulnerabilities. The number of vulnerabilities have also declined over the past four years, while Microsoft’s operating systems do not display the same trend, according to NIST’s national vulnerability database.

Since Linux’s famous kernel is open source and transparent, it is possible to extrapolate that there are a greater number of potential vulnerability watchdogs compared to those monitoring vulnerabilities in closed systems. Some may argue that Microsoft has been, at times, less successful at detecting vulnerabilities and issuing much-needed patches.

However, Linux users still must remain vigilant.

“Still, for any of the Linux distributions, anyone using the early release candidates — RC1 in particular — should make sure that their own development or build process is undergoing change control, so that no mishaps will transfer the nasty bug into a production environment,”  said Schrader.

B. Cameron Gain

B. Cameron Gain first began writing about technology when he hacked the Commodore 64 family computer in the early 1980s and documented his exploit. Since his misspent youth, he has put his obsession with software development to better use by writing thousands of papers, manuals, and articles for both online and print. His byline has appeared in Wired, PCWorld, Technology Review, Popular Science, EEtimes, and numerous other media outlets.

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