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Date: Thu, 12 Jul 2018 20:07:51 -0300
From: Ernesto =?utf-8?Q?A=2E_Fern=C3=A1ndez?=
        <ernesto.mnd.fernandez@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org, "Xu, Wen" <wen.xu@gatech.edu>
Subject: Re: [PATCH] hfsplus: fix NULL dereference in hfsplus_lookup()
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 <20180712153311.71495c0ea5ba0115414f5301@linux-foundation.org>
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On Thu, Jul 12, 2018 at 03:33:11PM -0700, Andrew Morton wrote:
> On Thu, 12 Jul 2018 18:53:47 -0300 Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com> wrote:
> 
> > Check that the hidden directory is not NULL before using it, instead of
> > after.
> > 
> 
> Under what circumstances does the crash happen?  Mount of a corrupted fs?

No, when looking up corrupted catalog data (dentry) on a filesystem with
no metadata directory (this could only ever happen on a read-only mount).
Wen Xu sent the replication steps in detail to the fsdevel list, here is
a link:

https://bugzilla.kernel.org/show_bug.cgi?id=200297

I did not explain this because I think the diff makes it clear that there
is a bug at least.