linux-kernel - Re: + c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-update-after-mm- num_exe_file

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Message-ID: <20120419222950.GA5807@redhat.com>
Date:	Fri, 20 Apr 2012 00:29:50 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"matthltc@...ibm.com" <matthltc@...ibm.com>,
	"tj@...nel.org" <tj@...nel.org>,
	Pavel Emelianov <xemul@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: 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

On 04/20, Konstantin Khlebnikov wrote:
>
>>> 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?

OK, if you do not see a problem - I agree with this patch.

I don't really understand what PR_SET_MM_EXE_FILE buys us if
parent/child can have different /proc/pid/exe links without
exec, but

> Actually I don't care too.

same here ;)

and at least this addresses the "establishes a bound on how
frequently the symlink can change" from Matt.

Oleg.

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