Meltdown/Spectre: Unauthorized Disclosure of Kernel Memory

Message

luiztux · Post by **luiztux** » Wed Jan 03, 2018 4:05 pm

ADMIN EDIT: Please see Project:Security/Vulnerabilities/Meltdown and Spectre for details. --pjp

Hey guys, did you see this?

https://lkml.org/lkml/2017/12/4/709

https://www.google.com.br/amp/s/amp.red ... _incoming/

Fitzcarraldo · Post by **Fitzcarraldo** » Wed Jan 03, 2018 4:29 pm

Happened to see this article in today's Guardian (UK) newspaper:

https://www.theguardian.com/technology/ ... c-os-linux

Haven't looked around yet. Anyone know anything more, and when firmware updates -- I assume Intel will be fixing this via firmware updates -- will be available?

Myu · Post by **Myu** » Wed Jan 03, 2018 5:17 pm

Not fixable by microcode

Linux 4.14.11 contains the KPTI (Kernel page table isolation) patch developped by Intel which incurs a performance hit (between 5 and 50%) to all Intel CPU users under certain workloads (syscalls will be slower)

https://www.reddit.com/r/sysadmin/comme ... _incoming/

I'm not that old so this is the biggest mess I've ever seen in the IT world I guess

For reference, the kernel config option seems to be CONFIG_PAGE_TABLE_ISOLATION=y

Edit : there it is, I am on 4.14.11 ...*sigh*

Code: Select all

cat /proc/cpuinfo | grep -i insecure
bugs		: cpu_insecure
bugs		: cpu_insecure
bugs		: cpu_insecure
bugs		: cpu_insecure
bugs		: cpu_insecure
bugs		: cpu_insecure
bugs		: cpu_insecure
bugs		: cpu_insecure

Also, nvidia-drivers-387.34 doesn't compile anymore with 4.14.11

Code: Select all

FATAL: modpost: GPL-incompatible module nvidia.ko uses GPL-only symbol 'cpu_tlbstate'
make[3]: *** [/usr/src/linux-4.14.11-gentoo/scripts/Makefile.modpost:92: __modpost] Error 1

eccerr0r · Post by **eccerr0r** » Wed Jan 03, 2018 7:53 pm

Lots of conflicting info out there, I think the "leak" is not a leak but accidental pseudo-privilege escalation which could result in information leakage. This is somewhat bad... however I hope I can continue to run it the way it has been running as an option for "internal" servers.

Sounds like this affects certain CPUs and perhaps only the Core-X CPUs, unsure about P4 or older.

On the bright side, from the sound of it, if you're using 32-bit and PAE, you won't see a performance hit...

khayyam · Post by **khayyam** » Wed Jan 03, 2018 8:11 pm

Fitzcarraldo ...

more detailed information on packetstorm (though the actual exploit remains undisclosed).

best ... khay

Tony0945 · Post by **Tony0945** » Wed Jan 03, 2018 8:35 pm

Watch out when updating your kernel if you have an AMD chip. Once you enable PAGE_TABLE_ISOLATION via make oldconfig you can;t turn it off with make menuconfig.

I wondered why my Athlon II was suddenly really slow launching X. I had to reboout with 4.14-10-r1 and update it again to 4.14.11 to choose "n" instead of "y" in make oldconfig.

Unless someone knows that this is needed for AMD too. Other sources on the web say this is for Intel only not AMD. But I'd like to hear it from our kernel experts.

Watcom · Post by **Watcom** » Wed Jan 03, 2018 9:36 pm

Apparently it affects every Intel CPU from the Pentium Pro onwards. Excluding the Pentium MMX which was released after the Pentium Pro in 1997.

AMD claims their CPUs are not affected, though we can only be sure after they disclose the actual bug details.

It looks quite serious though:
https://twitter.com/brainsmoke/status/9 ... 9875502080

PrSo · Post by **PrSo** » Wed Jan 03, 2018 10:12 pm

In the meantime:
https://newsroom.intel.com/news/intel-r ... -findings/

and

https://phoronix.com/scan.php?page=news ... le-x86-PTI

Tony0945 · Post by **Tony0945** » Wed Jan 03, 2018 10:17 pm

PrSo wrote:In the meantime:
https://newsroom.intel.com/news/intel-r ... -findings/

P.R. damage control.

PrSo · Post by **PrSo** » Wed Jan 03, 2018 10:23 pm

Tony0945 wrote:
PrSo wrote:In the meantime:
https://newsroom.intel.com/news/intel-r ... -findings/
P.R. damage control.

exactly:

http://www.nasdaq.com/symbol/intc

1clue · Post by **1clue** » Wed Jan 03, 2018 10:29 pm

It would be really neat if they fixed the bug with gcc 6.4 and recent kernels. The combination of this bug and the backported kernels is really unfortunate right now.

Naib · Post by **Naib** » Wed Jan 03, 2018 10:32 pm

PrSo wrote:In the meantime:
https://newsroom.intel.com/news/intel-r ... -findings/

and

https://phoronix.com/scan.php?page=news ... le-x86-PTI

https://www.barrons.com/articles/amd-sa ... 1515016135

AMD Says ‘Near Zero Risk’ to Its Chips

I am playing around with rc6 to see the impact when running some large simulation BUT I am not seeing any significant degradation

uname -a && cat /proc/cmdline

Linux fluidmotion 4.15.0-rc6 #1 SMP PREEMPT Wed Jan 3 16:07:25 GMT 2018 x86_64 AMD Ryzen 5 1600 Six-Core Processor AuthenticAMD GNU/Linux

BOOT_IMAGE=/vmlinuz-4.15.0-rc6 root=/dev/nvme0n1p2 ro video=uvesafb:1280x1024-32,mtrr:3,ywrap quiet splash libata.force=6.0 rootfstype=ext4 elevator=noop processor.max_cstate=5 pti=on

cat /proc/cpuinfo
...
bugs : sysret_ss_attrs null_seg cpu_insecure

so as expected bugs = cpu_insecure when pti=on is set YET...

uname -a && cat /proc/cmdline

Linux fluidmotion 4.15.0-rc6 #1 SMP PREEMPT Wed Jan 3 16:07:25 GMT 2018 x86_64 AMD Ryzen 5 1600 Six-Core Processor AuthenticAMD GNU/Linux

BOOT_IMAGE=/vmlinuz-4.15.0-rc6 root=/dev/nvme0n1p2 ro video=uvesafb:1280x1024-32,mtrr:3,ywrap quiet splash libata.force=6.0 rootfstype=ext4 elevator=noop processor.max_cstate=5 pti=off

cat /proc/cpuinfo
....
bugs : sysret_ss_attrs null_seg cpu_insecure

with pti=off the bug is still declared, its like it isn't being turned off in my test...

PrSo · Post by **PrSo** » Wed Jan 03, 2018 10:58 pm

@Naib
agreed.

IMHO I dont think that AMD devs are lying or hiding something.
Tom Lendacky is an architect in the CPU software group on AMD and I think he knows what his statement means.

My netbook has AMD cpu, kernel 4.14.11 from repo.

I turned PTI in kernel config off, and applied patch from LKML through

Code: Select all

/etc/portage/patches/sys-kernel/gentoo-sources/

lscpu or cat /proc/cpuinfo does not show any comment that my cpu is bugged.

Zephyrus · Post by **Zephyrus** » Wed Jan 03, 2018 11:29 pm

It seems that the details have now been publicly published, see for instance https://meltdownattack.com/ and https://googleprojectzero.blogspot.de/2 ... -side.html .

Atom2 · Post by **Atom2** » Wed Jan 03, 2018 11:37 pm

I have just received the following Xen Security Advisory by E-Mail. In a nutshell there are three types of vulnerabilities listed, two of which are relevant for both AMD and Intel.

The third vulnerability is an Intel only issue, but, under Xen, is only relevant for 64 bit PV guests. Xen PVH and HVM guests are not affected by the third issue.

At the moment, there is no confirmed information available whether ARM is vulnerable or not.

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

Xen Security Advisory XSA-254

Information leak via side effects of speculative execution

ISSUE DESCRIPTION
=================

Processors give the illusion of a sequence of instructions executed
one-by-one. However, in order to most efficiently use cpu resources,
modern superscalar processors actually begin executing many
instructions in parallel. In cases where instructions depend on the
result of previous instructions or checks which have not yet
completed, execution happens based on guesses about what the outcome
will be. If the guess is correct, execution has been sped up. If the
guess is incorrect, partially-executed instructions are cancelled and
architectural state changes (to registers, memory, and so on)
reverted; but the whole process is no slower than if no guess had been
made at all. This is sometimes called "speculative execution".

Unfortunately, although architectural state is rolled back, there are
other side effects, such as changes to TLB or cache state, which are
not rolled back. These side effects can subsequently be detected by
an attacker to determine information about what happened during the
speculative execution phase. If an attacker can cause speculative
execution to access sensitive memory areas, they may be able to infer
what that sensitive memory contained.

Furthermore, these guesses can often be 'poisoned', such that attacker
can cause logic to reliably 'guess' the way the attacker chooses.
This advisory discusses three ways to cause speculative execution to
access sensitive memory areas (named here according to the
discoverer's naming scheme):

SP1, "Bounds-check bypass": Poison the branch predictor, such that
operating system or hypervisor code is speculatively executed past
boundary and security checks. This would allow an attacker to, for
instance, cause speculative code in the normal hypercall / emulation
path to execute with wild array indexes.

SP2, "Branch Target Injection": Poison the branch predictor.
Well-abstracted code often involves calling function pointers via
indirect branches; reading these function pointers may involve a
(slow) memory access, so the CPU attempts to guess where indirect
branches will lead. Poisoning this enables an attacker to
speculatively branch to any code that exists in the hypervisor.

SP3, "Rogue Data Load": On some processors, certain pagetable
permission checks only happen when the instruction is retired;
effectively meaning that speculative execution is not subject to
pagetable permission checks. On such processors, an attacker can
speculatively execute arbitrary code in userspace with, effectively,
the highest privilege level.

More information is available here:
https://meltdownattack.com/
https://spectreattack.com/

Additional Xen-specific background:

64-bit Xen hypervisors on systems with less than 5TiB of RAM map all
of physical RAM, so code speculatively executed in a hypervisor
context can read all of system RAM.

When running PV guests, the guest and the hypervisor share the address
space; guest kernels run in a lower privilege level, and Xen runs in
the highest privilege level. (HVM and PVH guests run in a separate
address space to the hypervisor.) However, only 64-bit PV guests can
generate addresses large enough to point to hypervisor memory.

IMPACT
======

Xen guests may be able to infer the contents of arbitrary host memory,
including memory assigned to other guests.

An attacker's choice of code to speculatively execute (and thus the
ease of extracting useful information) goes up with the numbers. For
SP1, or SP2 on systems where SMEP (supervisor mode execute protection)
is enabled: an attacker is limited to windows of code after bound
checks of user-supplied indexes. For SP2 without SMEP, or SP3, an
attacker can write arbitrary code to speculatively execute.

NOTE ON TIMING
==============

This vulnerability was originally scheduled to be made public on 9
January. It was accelerated at the request of the discloser due to
one of the issues being made public.

VULNERABLE SYSTEMS
==================

Systems running all versions of Xen are affected.

For SP1 and SP2, both Intel and AMD are vulnerable.

For SP3, only Intel processors are vulnerable. Furthermore, only
64-bit PV guests can exploit SP3 against Xen. PVH and 32-bit PV
guests cannot exploit SP3.

We believe that ARM is affected, but unfortunately due to the
accelerated schedule, we haven't been able to get concrete input from
ARM. We are asking ARM and will publish more information when it is
available.

MITIGATION
==========

There is no mitigation for SP1 and SP2.

SP3 can be mitigated by running guests in HVM or PVH mode.

For guests with legacy PV kernels which cannot be run in HVM mode, we
have developed a "shim" hypervisor that allows PV guests to run in PVH
mode. Unfortunately, due to the accelerated schedule, this is not yet
ready to release. We expect to have it ready for 4.10, as well as PVH
backports to 4.9 and 4.8, available over the next few days.

RESOLUTION
==========

There is no available resolution for SP1 or SP3.

We are working on patches which mitigate SP2 but these are not
currently available. Given that the vulnerabilities are now public,
these will be developed and published in public, initially via
xen-devel.

When we have useful information we will send an update.

NOTE ON LACK OF EMBARGO
=======================

The timetable and process were set by the discloser.

After the intensive initial response period for these vulnerabilities
is over, we will prepare and publish a full timeline, as we have done
in a handful of other cases of significant public interest where we
saw opportunities for process improvement.
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Regards Atom2

PrSo · Post by **PrSo** » Wed Jan 03, 2018 11:47 pm

https://spectreattack.com/spectre.pdf

"Unlike Meltdown, the Spectre attack works on non-Intel processors, including AMD and ARM processors. Furthermore the KAISER patch, which has been widely applied as a mitigation to Meltdown attack, deos not protect against Spectre."

depontius · Post by **depontius** » Wed Jan 03, 2018 11:54 pm

So at the moment there is no protection for Spectre? Has anyone contacted James Bond?

Post by Hu » Wed Jan 03, 2018 11:59 pm

Myu: as I understand it, the initial iteration declares effectively all x86 CPUs to be affected, without trying to determine false positives. Some may not be impacted, although the speculation suggests that if you are on an Intel chip from within recent memory, you are impacted. An AMD employee asserts on LKML that AMD is unaffected. I have not seen any independent confirmation or refutation of that assertion.

Ralphred · Post by **Ralphred** » Thu Jan 04, 2018 12:03 am

Hu wrote:I have not seen any independent confirmation or refutation of that assertion.

There is a statement from AMD floating around which, at this time, says "we aren't committing to anything yet, but expect something by the end of the day" and something about waiting for researchers before commenting officially.

Ralphred · Post by **Ralphred** » Thu Jan 04, 2018 12:07 am

1clue wrote:It would be really neat if they fixed the bug with gcc 6.4 and recent kernels. The combination of this bug and the backported kernels is really unfortunate right now.

I appreciate anecdotal evidence is mostly useless, but just built 4.14.11 with 6.4 and it's working fine, nothing funky other than the ~amd64 for the kernel in package.use

mike155 · Post by **mike155** » Thu Jan 04, 2018 12:09 am

There are 2 different types of bugs: https://spectreattack.com/

The site provides scientific papers with details.

KAMIKAZE_ · Post by **KAMIKAZE_** » Thu Jan 04, 2018 2:50 am

Thanks, Intel, now I've made my decision: going AMD Ryzen Threadripper.

barophobia · Post by **barophobia** » Thu Jan 04, 2018 4:46 am

Thanks, Intel, now I've made my decision: going AMD Ryzen Threadripper.

AMD, Intel and ARM are all effected by the spectre attack. Different attack but still scary as hell.

eccerr0r · Post by **eccerr0r** » Thu Jan 04, 2018 5:36 am

I need to dig up my ia64 box...

Ant P. · Post by **Ant P.** » Thu Jan 04, 2018 9:23 am

They say there's no workaround, but there is: don't run arbitrary code off the network!

This is basic security! Everyone should have NoScript/uMatrix plus an adblocker at a bare minimum after Rowhammer.

Meltdown/Spectre: Unauthorized Disclosure of Kernel Memory

Meltdown/Spectre: Unauthorized Disclosure of Kernel Memory

Major security flaw found in Intel processors