linux-kernel - Re: [PATCH] vfs: use kstrdup()

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Message-ID: <20080721070346.GA28946@ZenIV.linux.org.uk>
Date:	Mon, 21 Jul 2008 08:03:46 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vfs: use kstrdup()

On Mon, Jul 21, 2008 at 02:29:47PM +0800, Li Zefan wrote:
> > FWIW, it _is_ a good question.
> > 
> > 	* is all code treating ->mnt_devname as optional?  AFAICS, there's
> > at least one place in NFS that doesn't.  We could treat failing allocation
> > the same way we treat failing allocation of vfsmount itself - callers can
> > cope with that already.
> 
> I just did a cleanup, and the original code didn't check for NULL.

I know.

> I just looked into the git history, and I found out since fs/namespace.c was
> created in v2.4.10.4, the code has never changed to check for failing
> allocation of ->mnt_devname.

It used to have no users beyond fs/namespace.c itself and for _those_ the
thing had been optional, so leaving NULL had been OK.  Unfortunately, it
still had been a bad idea - new users had appeared and those predictably
didn't notice that fun detail.

The right thing here is to consider failing allocation of ->mnt_devname
as failure of the entire alloc.
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