lkml.org 
[lkml]   [2020]   [Sep]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v12 1/8] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking
From
Date
On 9/18/2020 1:59 PM, Pavel Machek wrote:
> On Fri 2020-09-18 13:24:13, Randy Dunlap wrote:
>> Hi,
>>
>> If you do another version of this:
>>
>> On 9/18/20 12:23 PM, Yu-cheng Yu wrote:
>>> Introduce Kconfig option X86_INTEL_BRANCH_TRACKING_USER.
>>>
>>> Indirect Branch Tracking (IBT) provides protection against CALL-/JMP-
>>> oriented programming attacks. It is active when the kernel has this
>>> feature enabled, and the processor and the application support it.
>>> When this feature is enabled, legacy non-IBT applications continue to
>>> work, but without IBT protection.
>>>
>>> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
>>> ---
>>> v10:
>>> - Change build-time CET check to config depends on.
>>>
>>> arch/x86/Kconfig | 16 ++++++++++++++++
>>> 1 file changed, 16 insertions(+)
>>>
>>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>>> index 6b6dad011763..b047e0a8d1c2 100644
>>> --- a/arch/x86/Kconfig
>>> +++ b/arch/x86/Kconfig
>>> @@ -1963,6 +1963,22 @@ config X86_INTEL_SHADOW_STACK_USER
>>>
>>> If unsure, say y.
>>>
>>> +config X86_INTEL_BRANCH_TRACKING_USER
>>> + prompt "Intel Indirect Branch Tracking for user-mode"
>>> + def_bool n
>>> + depends on CPU_SUP_INTEL && X86_64
>>> + depends on $(cc-option,-fcf-protection)
>>> + select X86_INTEL_CET
>>> + help
>>> + Indirect Branch Tracking (IBT) provides protection against
>>> + CALL-/JMP-oriented programming attacks. It is active when
>>> + the kernel has this feature enabled, and the processor and
>>> + the application support it. When this feature is enabled,
>>> + legacy non-IBT applications continue to work, but without
>>> + IBT protection.
>>> +
>>> + If unsure, say y
>>
>> If unsure, say y.
>
> Actually, it would be "If unsure, say Y.", to be consistent with the
> rest of the Kconfig.
>
> But I wonder if Yes by default is good idea. Only very new CPUs will
> support this, right? Are they even available at the market? Should the
> help text say "if your CPU is Whatever Lake or newer, ...." :-) ?

I will revise the wording if there is another version. But a
CET-capable kernel can run on legacy systems. We have been testing that
combination.

Yu-cheng

\
 
 \ /
  Last update: 2020-09-18 23:26    [W:0.074 / U:0.448 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site