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Date: Thu, 6 Oct 2016 23:41:17 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Sinan Kaya <okaya@codeaurora.org>
Cc: timur@codeaurora.org, cov@codeaurora.org,
        linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Revert "debugfs: ->d_parent is never NULL or negative"
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On Thu, Oct 06, 2016 at 11:37:29PM +0100, Al Viro wrote:

> If you ever get NULL in ->d_parent of struct dentry instance, you are
> practically certain to have a dangling pointer to memory that used to
> contain a struct dentry at some point but got freed and reused since then.

... which is what happens in your case, apparently.  ->stats is still
pointing to a dentry that had just been freed and its memory reused.