Linus Torvalds’ Precious Advice to Security Experts

Nov 28, 2017

Torvalds said that developers should focus more on debugging than resorting to fallback mode.

Linus Torvalds, the creator of the Linux kernel, is no fan of the security community. In his opinion security is just bugs that get exploited. “I don’t trust security people to do sane things,” said Torvalds, responding to a merge request by one of the top kernel developers Kees Cook.

What ticked Torvalds off this time was that Kees’ patch had the potential to break things, and he added a fallback mode. Kees wrote, “This has lived in -next for quite some time without major problems, but there were some late-discovered missing whitelists, so a fallback mode was added just to make sure we don’t break anything. I expect to remove the fallback mode in a release or two.”

Torvalds refused to merge and said, “If you can make a smaller pull request that introduces the infrastructure, but that _obviously_ cannot actually break anything, that would be more likely to be palatable.”

To which Kees responded, “This is why I introduced the fallback mode: with both kvm and sctp (ipv6) not noticed until late in the development cycle, I became much less satisfied it had gotten sufficient testing. I wanted to make sure there was a way for the series to land without actually breaking things due to any missed whitelists.”

Torvalds said, “I’m not at all interested in killing processes. The only process I’m interested in is the _development_ process, where we find bugs and fix them.”

But this time Torvalds has a valuable piece of advice for security people. He said that the primary focus should be “debugging” and making sure the kernel released in a year is better than the one released today. He dismissed the popular notion of kill processes for bugs. “… the hardening efforts should instead _start_ from the standpoint of ‘let’s warn about what looks dangerous, and maybe in a _year_ when we’ve warned for a long time, and we are confident that we’ve actually caught all the normal cases, _then_ we can start taking more drastic measures’,” said Torvalds, “Stop this idiotic ‘kill on sight, ask questions later’.”

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