linux-kernel - Re: cgroup_release_agent() with call_usermodehelper() with UMH_WAIT

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Message-ID: <CA+55aFx0SxW5ST2H1TL6K-457nP1qtAva0+YcnJLNoUUz_PCdg@mail.gmail.com>
Date:	Fri, 3 Feb 2012 08:48:08 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <paul@...lmenage.org>,
	linux-kernel@...r.kernel.org,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>
Subject: Re: cgroup_release_agent() with call_usermodehelper() with
 UMH_WAIT_EXEC may crash

On Fri, Feb 3, 2012 at 8:04 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>
> Can't we simply move that code into flush_old_exec() ? (wrapped into
> the new helper).

Sure. It would kind of make sense to do it as part of exec_mmap().
That's what associates us with the new mm, after all.

That said, I think my *preferred* approach would be to still do the final

    set_task_comm(current, tcomm);

in setup_new_exec(), because that's really when we set up the new mm.

So my preferred solution would be to simply move the "char tcomm[];"
array from the stack (currently automatic in setup_new_exec()) into
the struct linux_binprm, and then copy it from the filename early. We
could copy it arbitrarily early, perhaps in "prepare_binprm()".

Hmm?

                       Linus
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