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: Konstantin Khlebnikov
Date: Thu Apr 19 2012 - 18:08:59 EST

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

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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