From: Jan Kara <jack@suse.cz>
To: Chen Gang <gang.chen@asianux.com>
Cc: Theodore Ts'o <tytso@mit.edu>,
jack@suse.cz, akpm@linux-foundation.org,
linux-ext4@vger.kernel.org
Subject: Re: [PATCH] fs/ext3: set pointer = NULL, after kfree it
Date: Mon, 31 Dec 2012 16:19:53 +0100 [thread overview]
Message-ID: <20121231151953.GE7564@quack.suse.cz> (raw)
In-Reply-To: <50DA61E8.5090009@asianux.com>
On Wed 26-12-12 10:33:12, Chen Gang wrote:
> 于 2012年12月26日 02:51, Theodore Ts'o 写道:
> > On Mon, Dec 24, 2012 at 01:58:14PM +0800, Chen Gang wrote:
> >>
> >> set s->base = NULL, after kfree it.
> >>
> >> Signed-off-by: Chen Gang <gang.chen@asianux.com>
> >
> > Was this to fix something flagged by some static code checker? The
> > only caller of ext3_xattr_block_set() is ext3_xattr_set_handle(), and
> > s->base is stored on the stack, and as soon as ext3_xattr_block_set()
> > returns, the object will disappear. So it seems pretty hard to see
> > how this could lead to a use-after-free bug.
> >
> > - Ted
> >
> >
>
> this patch is not for a bug
>
> it is only for coding habit:
> it is better to set is to NULL, after kfree it.
> in the future, if another functions need call ext3_xattr_block_set, too.
> it will avoid another members to make mistake.
Well, we set pointers to NULL after kfree() only if there's a good chance
we ever look at the pointer again. This is not the case so I don't think
this change makes the code any more safer / easier to read.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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prev parent reply other threads:[~2012-12-31 15:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-24 5:58 [PATCH] fs/ext3: set pointer = NULL, after kfree it Chen Gang
2012-12-25 18:51 ` Theodore Ts'o
2012-12-26 2:33 ` Chen Gang
2012-12-31 15:19 ` Jan Kara [this message]
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