Re: +c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-update-after-mm-num_exe_file_vmas-removal.patch added to -mm tree

From: Cyrill Gorcunov
Date: Thu Apr 19 2012 - 17:00:40 EST

On Thu, Apr 19, 2012 at 09:20:05PM +0200, Oleg Nesterov wrote:
> On 04/19, Andrew Morton wrote:
> >
> > From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
> > Subject: c/r: prctl: update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal
> >
> > [ fix for "c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-v2" from mm tree ]
> >
> > After removing mm->num_exe_file_vmas kernel keeps mm->exe_file until final
> > mmput(), it never becomes NULL while task is alive.
> >
> > We can check for other mapped files in mm instead of checking
> > mm->num_exe_file_vmas, and mark mm with flag MMF_EXE_FILE_CHANGED in order
> > to forbid second changing of mm->exe_file.
> I lost the track a long ago.
> Just one question, what does this "forbid second changing" actually mean?

Heh :) Oleg, it was actually your idea to make this feature "one-shot".
Once exe-file changed to a new value, it can't be changed again. The
reason was to bring at least minimum disturbance in sysadmins life.

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