[lkml]   [2012]   [Feb]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH][GIT PULL][v3.3] x86: Test saved %rip in NMI to determine nested NMI
On 02/19/2012 12:34 PM, Steven Rostedt wrote:
> On Sun, 2012-02-19 at 05:46 -0800, wrote:
>> Vsyscall page, not vdso...
> Peter,
> My original patch was to check the %cs register against __KERNEL_CS, but
> IIRC, you said that userspace can change that register to anything it
> wanted before doing a long jump or something. Is this true for x86_64 as
> well? I guess it would be because x86_64 can support 32bit apps.
> Anyway, I'll add a check that makes sure that the RIP is less than the
> FIXADDR sections as well.

User space can change %cs, but it can never set it to __KERNEL_CS;
specifically user space can never set the bottom two bits in CS to zero.

So this should be a better test.

(Now, doing the test that way plays havoc with the braindamage knows as
Xen paravirt, but I don't think it's subject to this particular NMI code.)


 \ /
  Last update: 2012-02-19 21:49    [W:0.054 / U:3.664 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site