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Date: Fri, 24 Mar 2023 13:44:34 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Matthew Wilcox <willy@infradead.org>, <linux-fsdevel@vger.kernel.org>,
 <nvdimm@lists.linux.dev>, <dan.j.williams@intel.com>, <jack@suse.cz>,
 <djwong@kernel.org>
Subject: Re: [PATCH] fsdax: unshare: zero destination if srcmap is HOLE or
 UNWRITTEN
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On Fri, 24 Mar 2023 12:28:07 +0800 Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote:

> > ie it's the data that was in whatever file happened to use that space
> > last, so this is a security bug because it's a data leak, and a backport
> > is needed, and you should have indicated that by putting a cc: stable
> > tag on the patch?
> 
> Yes, cc stable is needed.  Then should I send a new patch with the tag 
> added?

Thanks.  I updated the changelog and added cc:stable.

: unshare copies data from source to destination.  But if the source is
: HOLE or UNWRITTEN extents, we should zero the destination, otherwise
: the HOLE or UNWRITTEN part will be user-visible old data of the new
: allocated extent because it wasn't cleared.
: 
: Found by running generic/649 while mounting with -o dax=always on pmem.