linux-kernel - Re: [PATCH] kernel/delayacct.c: check NULL for member variable 'delays' in all extern functions.

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Message-Id: <20130821151025.77673f0f3cad748a80086a16@linux-foundation.org>
Date:	Wed, 21 Aug 2013 15:10:25 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	bsingharora@...il.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel/delayacct.c: check NULL for member variable
 'delays' in all extern functions.

On Tue, 20 Aug 2013 10:40:03 +0800 Chen Gang <gang.chen@...anux.com> wrote:

> The member variable 'delays' may be NULL, so need check NULL before use
> it for all extern functions, just like __delayacct_tsk_init() and
> __delayacct_add_tsk() have already done.

If task.delays is NULL, the kernel will oops.  I don't recall seeing
such oops reports hence I suspect that you missed some check somewhere.

For example, delayacct_blkio_start() checks current->delays before
calling __delayacct_blkio_start(), so why retest current->delays in
__delayacct_blkio_start()?
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