lkml.org 
[lkml]   [2015]   [Jul]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 0/4] x86: modify_ldt improvement, test, and config option
On 07/31/2015 05:10 AM, Andrew Cooper wrote:
> On 30/07/15 22:31, Andy Lutomirski wrote:
>> This is intended for x86/urgent. Sorry for taking so long, but it
>> seemed nice to avoid breaking Xen.
> Very much appreciated. Thanks!
>
>> This fixes the "dazed and confused" issue which was exposed by the
>> CVE-2015-5157 fix. It's also probably a good general attack surface
>> reduction, and it replaces some scary code with IMO less scary code.
>>
>> Also, servers and embedded systems should probably turn off modify_ldt.
>> This makes that possible.
>>
>> Xen people, can you test patch 1? It works for me on my evil 32-bit
>> Xen virtio setup.
> So the LDT issue seems to have gone away, which is good.
>
> However, I did get this from my single vcpu guest test
>
> [OK] LDT entry 0 is invalid
> [SKIP] Cannot set affinity to CPU 1
> [RUN] Test exec
> [ 3.638967] CPU 0 set the LDT
> [OK] LDT entry 0 has AR 0x0040FA00 and limit 0x0000002A
> [ 3.639380] ------------[ cut here ]------------
> [ 3.639389] WARNING: CPU: 0 PID: 383 at
> /local/linux-mainline.git/arch/x86/include/asm/mmu_context.h:96
> flush_old_exec+0x7fd/0xb70()
> [ 3.639397] DEBUG_LOCKS_WARN_ON(!irqs_disabled())

You must be running v5 (or earlier). This is fixed in v6 --- it is now
'DEBUG_LOCKS_WARN_ON(preemptible());'


-boris


\
 
 \ /
  Last update: 2015-07-31 16:01    [W:0.170 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site