linux-kernel - Re: [PATCH 0/1] wait: using uninitialized member of wait queue

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Message-ID: <AANLkTimEp8rorHxtOQji-xtXZoDkcYrGGWCBQg3ypKf4@mail.gmail.com>
Date:	Tue, 5 Oct 2010 08:43:15 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Evgeny Kuznetsov <EXT-Eugeny.Kuznetsov@...ia.com>
Cc:	akpm@...ux-foundation.org, m.nazarewicz@...sung.com, mingo@...e.hu,
	gregkh@...e.de, a.p.zijlstra@...llo.nl, xiaosuo@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/1] wait: using uninitialized member of wait queue

On Tue, Oct 5, 2010 at 1:47 AM, Evgeny Kuznetsov
<EXT-Eugeny.Kuznetsov@...ia.com> wrote:
>
> Here is patch which fixes bug in /include/linux/wait.h file.
> Member "flags" of "wait_queue_t" struct  is used in several places in
> kernel code without beeing initialized. "flags" is used in bitwise
> operations. If it contain dummy data then incorrect flags may be
> used later in code.

The patch looks fine, but do you have any case of this actually
causing problems? Afaik, we do end up initializing the part of the
flags field we care about (WQ_FLAG_EXCLUSIVE) in prepare_to_wait()
(and add_wait_queue()), so it looks - from an admittedly very cursory
read - as if this is a good cleanup but shouldn't actually be the
cause of any actual bugs.

So I'll apply it, but I just wondered if you had actually seen any
semantic changes from it?

               Linus
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