linux-kernel - Re: [PATCH] exit signals: use of uninitialized field notify

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Message-ID: <alpine.DEB.1.00.0808271747160.15543@abydos.NerdBox.Net>
Date:	Wed, 27 Aug 2008 17:58:17 -0700 (PDT)
From:	Steve VanDeBogart <vandebo-lkml@...dBox.Net>
To:	Oleg Nesterov <oleg@...sign.ru>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Roland McGrath <roland@...hat.com>
Subject: Re: [PATCH] exit signals: use of uninitialized field notify_count

On Wed, 27 Aug 2008, Oleg Nesterov wrote:

>> * Steve VanDeBogart <vandebo-lkml@...dBox.Net> wrote:
>>
>>> task->signal->notify_count is only initialized if
>>> task->signal->group_exit_task is not NULL.  Reorder a conditional so
>>> that uninitialised memory is not used.  Found by Valgrind.
>
> Minor comment. As Roland pointed out, it makes sense to initialize
> the whole signal_struct explicitely, perhaps copy_signal() should
> just use zalloc. In that case we don't need to check ->group_exit_task
> at all, the same for __exit_signal().
>
> Thanks Steve! and what do you think about the above?

It looks like that would work.  Seems that
sig->count == 0 && sig->group_exit_task != NULL can never be true.
If it does work, a lot of initialization in copy_signal() can be
removed and it would reduce the chances that a similar problem would be
reintroduced.  I would submit a patch, but I'm not sure how to trigger
those code paths in order to test it.

--
Steve
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