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The mysterious case of the Linux Page Table Isolation patches

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Re: The mysterious case of the Linux Page Table Isolation patches

#31

Post by revelation »

justincormack wrote: post #28
revelation wrote: post #22

Earlier quoted context omitted.

Well Intel for one manufactures the insecure CPUs.. This will be merged for 4.16, when there is no 4.15 release yet. No idea what your cloud computing companies run but it's not 4.15-dirty, and backporting this monster is a great recipe for a nightly emergency when it goes OOPS. edit: it isn't even merged yet.

It is being backported to 4.14, and presumably earlier kernel too.

Sure, with the appropriate baking time. But I don't see a cloud company taking an intermediate version of this patchset, backporting it themselves and then sending it out to all their customers in a hurry.

Re: The mysterious case of the Linux Page Table Isolation patches

#32

Post by amluto »

revelation wrote: post #22
saas_co_de wrote: post #13

Earlier quoted context omitted.

It sounds like Intel, Google and Amazon are hiding something. Wouldn't want customers thinking that cloud computing is fundamentally insecure now would we?

Well Intel for one manufactures the insecure CPUs.. This will be merged for 4.16, when there is no 4.15 release yet. No idea what your cloud computing companies run but it's not 4.15-dirty, and backporting this monster is a great recipe for a nightly emergency when it goes OOPS. edit: it isn't even merged yet.

Like the backports here?

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux...

Go test!

I agree, they're very scary. Also, watch out: a kernel with PTI on will not function in KVM-emulated secure boot mode until a KVM fix gets backported as well.

Re: The mysterious case of the Linux Page Table Isolation patches

#33

Post by avian »

userbinator wrote: post #20

IMHO, with RowHammer, the hardware is broken and it will continue to be broken until users complain enough --- maybe to the point of absolutely refusing to buy --- that the manufacturers and designers stop thinking "works 99.9999999999% of the time" is good enough: https://news.ycombinator.com/item?id=12410274

Why would users refuse to buy hardware that works 99.9999999999% of the time when they apparently have no problem buying software that works 99% of the time?

Radioactive decays and cosmic particles flipping bits give an upper bound for reliability. You are not going to see low-background packages and rad-hard chips in your iPhone.

Re: The mysterious case of the Linux Page Table Isolation patches

#34

Post by preordained »

syshum wrote: post #10
tbrownaw wrote: post #2

"Hey, I think I noticed a horrible horrible embargoed security bug. I know, I should do my best to pole holes in the embargo early!"

Ahh yes, Security through Obscurity that is always the best If no one talks about a security problem that makes it disappear

If you're taking off for vacation and forgot to lock your door, the best thing would be to go back and lock it. If you couldn't get the door locked right away for some reason, you probably wouldn't want the news of your unlocked door broadcast through your neighborhood...

Obscurity actually is a layer of security. The mistake is is when people are dependent upon it.

Re: The mysterious case of the Linux Page Table Isolation patches

#35

Post by KirinDave »

revelation wrote: post #30
geofft wrote: post #25

Earlier quoted context omitted.

The patchset being developed in the open, and the rationale for the development being done in the way it is, are two very different things.

But no one is hiding the bug this "fixes". If this bug + something else can be a hypervisor escape, well that's too bad for the AWS of this world, but I don't see how this patchset would leak the "something else" we don't know about?

It's not unusual for folks implementing popular OSs to get heads up that some sort of Significant Security Issue is being discussed by other vendors, including receiving advice.

I consider this newsworthy because many very good security engineers in my feed agree it is.

Re: The mysterious case of the Linux Page Table Isolation patches

#37

Post by userbinator »

avian wrote: post #33
userbinator wrote: post #20

IMHO, with RowHammer, the hardware is broken and it will continue to be broken until users complain enough --- maybe to the point of absolutely refusing to buy --- that the manufacturers and designers stop thinking "works 99.9999999999% of the time" is good enough: https://news.ycombinator.com/item?id=12410274

Why would users refuse to buy hardware that works 99.9999999999% of the time when they apparently have no problem buying software that works 99% of the time? Radioactive decays and cosmic particles flipping bits give an upper bound for reliability. You are not going to see low-background packages and rad-hard chips in your iPhone.

Radioactive decays and cosmic particles flipping bits give an upper bound for reliability well below 99.9999999999%

If it works 99.9999999999%, then it has a failure rate of 0.0000000001%, or 1E-12. Considering that a modern CPU executes approximately 1E9 operations per second, and that regular HDDs have a worse-case BER of 1 in 1E14 bits, 1E-12 is actually rather horrible and the actual error rate of computer hardware is much better than that.

Imagine if a CPU calculated 1+1=3 every 1E12 instructions. At current clock rates, that's a fraction of an hour. Computers simply would not work if CPUs had such an error rate.

I picked the 1E-12 number arbitrarily, but it's quite illustrative of the reliability computers are expected to have, despite their flaws.

Re: The mysterious case of the Linux Page Table Isolation patches

#38

Post by Nano2rad »

saas_co_de wrote: post #13
revelation wrote: post #7

No ones hiding anything, this patchset was developed in the open for many many months. The hysteria and intrigue in this random tumblr blog is completely superfluous. It's a hardware bug anyway. Here is a good hint to when something is not being embargoed: there is a paper and a public demonstration.

It sounds like Intel, Google and Amazon are hiding something. Wouldn't want customers thinking that cloud computing is fundamentally insecure now would we?

If it is hardware Microsoft also will be patching.

Re: The mysterious case of the Linux Page Table Isolation patches

#39

Post by avh02 »

saas_co_de wrote: post #11
tbrownaw wrote: post #2

"Hey, I think I noticed a horrible horrible embargoed security bug. I know, I should do my best to pole holes in the embargo early!"

Embargos do not make you secure. If the bug exists the only safe assumption is that it is already being exploited. The faster the information gets out the better.

No, but they prevent everybody with ill-intent from exploiting the issue en-masse

Re: The mysterious case of the Linux Page Table Isolation patches

#40

Post by hujji »

userbinator wrote: post #20

IMHO, with RowHammer, the hardware is broken and it will continue to be broken until users complain enough --- maybe to the point of absolutely refusing to buy --- that the manufacturers and designers stop thinking "works 99.9999999999% of the time" is good enough: https://news.ycombinator.com/item?id=12410274

The current miniaturization of DRAM circuitry doesn't really allow for a hardware fix for the RowHammer attack. During DRAM manufacturing a test similar to the RowHammer attack exists. This test has certain bounds for passing. If the bounds were tightened up to the level of perfection to prevent the attack it would drop the yield a considerable amount.
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