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Reading privileged memory with a side-channel

googleprojectzero.blogspot.com

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Re: Reading privileged memory with a side-channel

#21

Post by MBCook »

Cyph0n wrote: post #17
MBCook wrote: post #8

Earlier quoted context omitted.

See the Twitter thread here: https://twitter.com/nicoleperlroth/status/948678006859591682 (Edit: there are 9 posts total, go to her user page to see them all) Seems there are two issues. One, called Meltdown, only effects Intel and is REALLY bad, but the kernel page table changes everyone is making fixes it. The other, dubbed Spectre, is apparently common to the way all processors handle speculative execution and is…

That's not even close to a thread... You can see all the tweets here (courtesy of @svenluijten): https://twitter.com/i/moments/948681915485351938 .

I didn’t find out there were more than 4 posts until after I made my comment (thus the edit).

Thanks for the handy link.

Re: Reading privileged memory with a side-channel

#22

Post by static_noise »

So, as I gather, one of the main culprits is that unwinding of speculatively executed commands is done incompletely. That is something that the people doing the unwinding must have noticed and known. Somewhere the decision must have been made to unwind incompletely for some reasons (performance/power/cost/time).

As for the difference between AMD and intel. (From other posts here, not this one.) The speculative execution can access arbitrary memory locations on intel processors while this is not possible on AMD. This means that on intel processors you can probe any memory location with only limited privileges.

As for the affected AMD and ARM processors I'm none the wiser. How are they affected? Which models are affected? Does it allow some kind of privilege escalation? The next days will surely stay interesting.

Re: Reading privileged memory with a side-channel

#23

Post by userbinator »

btilly wrote: post #10
chrisb wrote: post #2

"These vulnerabilities affect many CPUs, including those from AMD, ARM, and Intel, as well as the devices and operating systems running them." Curious. All other reports I've read state that AMD CPUs are not vulnerable.

And yet it also says that AMD devices running Android are not vulnerable. I'd be curious how those two statements should be reconciled.

Not exactly; it says "we are unaware of any successful reproduction of this vulnerability that would allow unauthorized information disclosure on ARM-based Android devices."

Re: Reading privileged memory with a side-channel

#25

Post by MBCook »

noncoml wrote: post #6
chrisb wrote: post #2

"These vulnerabilities affect many CPUs, including those from AMD, ARM, and Intel, as well as the devices and operating systems running them." Curious. All other reports I've read state that AMD CPUs are not vulnerable.

We won't know until we have the full details. From the linux patches it looked like that AMD x86-64 processors were not affected. But the sentence you quote adds AMD back into play. Maybe some of its ARM processors? e.g. AMD Opteron A1100?

They weren’t effected by the really bad Intel big names Meltdown. They’re still susceptible to Spectre.

Re: Reading privileged memory with a side-channel

#26

Post by mrmondo »

MikeHolman wrote: post #20
mrmondo wrote: post #13

"AMD chips are affected by some but not all of the vulnerabilities. AMD said that there is a "near zero risk to AMD processors at this time." British chipmaker ARM told news site Axios prior to this report that some of its processors, including its Cortex-A chips, are affected." - http://www.zdnet.com/article/security-flaws-affect-every-int... * Edit: From https://meltdownattack.com/ Which systems are affected by Mel…

Looks like everyone is vulnerable to arbitrary user memory reads, while Intel and ARM are vulnerable to arbitrary kernel memory reads as well.

Thanks for clarifying Mike, should be interesting to see how this actually pans out.

Re: Reading privileged memory with a side-channel

#28

Post by AsyncAwait »

partiallypro wrote: post #16

So, is AMD effected or not? This seems fairly important. The Google blog post sort of goes against itself in this regard. AMD itself has said: "The threat and the response to the three variants differ by microprocessor company, and AMD is not susceptible to all three variants. Due to differences in AMD's architecture, we believe there is a near zero risk to AMD processors at this time." So either AMD is lying or Goog…

It seems like it is not affected by the most serious bug, but may be by a lesser one.

Re: Reading privileged memory with a side-channel

#29

Post by static_noise »

forgot-my-pw wrote: post #15
azurezyq wrote: post #9

Earlier quoted context omitted.

You can find the details below. They've tried AMD CPUs also. https://googleprojectzero.blogspot.com/2018/01/reading-privi...

"We reported this issue to Intel, AMD and ARM on 2017-06-01" What!

How much in advance do the intel managers have to register a stock sell?
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