Security Models for the Kernel – Harsh Words from Torvalds

Oct 04, 2007

A debate on various security models for the Linux kernel has developed on the Linux Kernel Mailing List.

The bone of contention was a suggestion by Andrew Morton to introduce the "Simplified Mandatory Access Control Kernel" (Smack) in kernel 2.6.24. Developer James Morris responded that the decision to introduce Smack had to be seen in the wider context of the kernel's security architecture. He did not criticize Smack itself, but the loadable module LSM, on which Smack is based; however, LSM is only used by SELinux, who also programmed Smack. LSM would have been removed long ago, part from this fact.

Linus Torvalds entered the discussion at this point, responding saying that LSM was staying "You security people are insane. I'm tired of this "only my version is correct" crap. The whole and only point of LSM was to get away from that." Torvalds continues: "I guess I have to merge AppArmor and SMACK just to get this *disease* off the table." Responding to this verbal attack, developer Stephen Smalley objects that Torvalds is normally against loadable schedulers, asking: "Why is security different??"

Torvalds' response is unequivocal: "Schedulers can be objectively tested. There's this thing called "performance" that can generally be quantified on a load basis." He continues, "Yes, you can have crazy ideas in both schedulers and security. Yes, you can simplify both for a particular load. Yes, you can make mistakes in both. But the *discussion* on security seems to never get down to real numbers. So the difference between them is simple: one is "hard science". The other one is "people w****g [expletive deleted] around with their opinions."

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