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

[Konstantin Khlebnikov]

Cyrill Gorcunov wrote:
> On Thu, Apr 19, 2012 at 11:12:16PM +0200, Oleg Nesterov wrote:
> > > Heh :) Oleg, it was actually your idea to make this feature "one-shot".
> >
> > Heh, no ;)
> >
> > IIRC, I only asked you what do you actually want,
> >
> > 	Just one note for the record, prctl_set_mm_exe_file() does
> >
> > 		if (mm->num_exe_file_vmas)
> > 			return -EBUSY;
> >
> > 	We could do
> >
> > 		if (mm->exe_file)
> > 			return -EBUSY;
> >
> > 	This way "because this feature is a special to C/R" becomes
> > 	really true. IOW, you can't do PR_SET_MM_EXE_FILE twice.
> >
> > 	I am fine either way, just I want to ensure you really want
> > 	the current version.
> >
> > and only because it was documented as "feature is a special to C/R".
>
> ok, ubedil :)
>
> > > 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.
> >
> > You misunderstood. I am not arguing with "one-shot", I do not really
> > care.
> >
> > My question is: unless I missed something "it can't be changed again"
> > is not actually true. A task does PR_SET_MM_EXE_FILE, then it forks
> > the new child. The child can do PR_SET_MM_EXE_FILE again. Is this
> > by design?
>
> Hmm, not sure, Konstantin?

Why not? It has new pid, why it cannot change exe_file? Actually I don't care too.
But even if we include this bit into MMF_INIT_MASK we cannot forbid exe-file change
in childs tasks which was forked before exe-file change in parent.
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