linux-kernel - Re: [PATCH v2] configfs: Fix use-after-free when accessing sd->s

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Message-ID: <20190517082312.GA13457@lst.de>
Date:   Fri, 17 May 2019 10:23:12 +0200
From:   Christoph Hellwig <hch@....de>
To:     stummala@...eaurora.org
Cc:     Junxiao Bi <junxiao.bi@...cle.com>,
        Joel Becker <jlbec@...lplan.org>,
        Christoph Hellwig <hch@....de>,
        Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] configfs: Fix use-after-free when accessing
 sd->s_dentry

On Thu, May 16, 2019 at 06:27:53PM +0530, stummala@...eaurora.org wrote:
> Hi Christoph, Al,
>
> Can you please consider this patch for merging?

I've been sitting on this for a while, mostly because I can't convince
myself it is safe.  What protects other threads from using ->s_dentry
just when we clear it?  Also why would sd->s_dentry == dentry ever be
false?