[Devel] [PATCH 2/2] parasite: Don't try to start executing syscall from guard page

[Cyrill Gorcunov]

On Thu, Nov 24, 2016 at 07:34:14PM +0300, Pavel Emelyanov wrote:
> On 11/24/2016 07:16 PM, Cyrill Gorcunov wrote:
> > On Thu, Nov 24, 2016 at 07:02:10PM +0300, Pavel Emelyanov wrote:
> >> On 11/24/2016 06:48 PM, Cyrill Gorcunov wrote:
> >>> When looking for place where we can do syscall we should care
> >>> if there a guard page present. So check for it first.
> >>
> >> Have we found a task with executable stack?
> > 
> > Not "stack" in classic meaning, but a special mmap which
> > kernels treats as a stack and adds guard page. It is our test maps05
> 
> Wait, kernel guards VMAs with MAP_GROWSDOWN, while CRIU searches for PROT_EXEC
> areas to work on. Have our test created such a mapping? I'd fix the test, no
> applications behave like that %)

Yes we do create such mapping and it's completely correct to applications
to create the same mappings. In reverse, I think it's good that we have
such test -- it is straight bug in criu, not test.