Messages in this thread | | | Date | Fri, 5 Jan 2018 12:12:41 +0000 | From | Alan Cox <> | Subject | Re: Avoid speculative indirect calls in kernel |
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On Fri, 5 Jan 2018 01:54:13 +0100 (CET) Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 4 Jan 2018, Jon Masters wrote: > > P.S. I've an internal document where I've been tracking "nice to haves" > > for later, and one of them is whether it makes sense to tag binaries as > > "trusted" (e.g. extended attribute, label, whatever). It was something I > > wanted to bring up at some point as potentially worth considering. > > Scratch that. There is no such thing as a trusted binary.
There is if you are using signing and the like. I'm sure SELiux and friends will grow the ability to set per process policy but that's certainly not a priority.
However the question is wrong. 'trusted' is a binary operator not a unary one.
The question that matters is
If I am executing A and about to switch to B does B trust A
because if B trusts A (which in Linuxspeak is 'can A ptrace B') then there's not much point worrying about protection between them because what you are trying to prevent is already expressly permitted.
It's even more important if there is a cost to the barrier imposition because not only can you skip it sometimes but your scheduler can schedule considering that cost just as it does cache eviction costs.
Alan
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