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Date: Thu, 23 Mar 2023 07:59:57 -0700
From: "Darrick J. Wong" <djwong@kernel.org>
To: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev,
	dan.j.williams@intel.com, willy@infradead.org, jack@suse.cz
Subject: Re: [PATCH] fsdax: unshare: zero destination if srcmap is HOLE or
 UNWRITTEN
Message-ID: <20230323145957.GA466461@frogsfrogsfrogs>
References: <1679483469-2-1-git-send-email-ruansy.fnst@fujitsu.com>
 <20230322160311.89efea3493db4c4ccad40a25@linux-foundation.org>
 <a41f0ea1-c704-7a2e-db6d-93e8bd4fcdea@fujitsu.com>
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In-Reply-To: <a41f0ea1-c704-7a2e-db6d-93e8bd4fcdea@fujitsu.com>

On Thu, Mar 23, 2023 at 02:50:38PM +0800, Shiyang Ruan wrote:
> 
> 
> 在 2023/3/23 7:03, Andrew Morton 写道:
> > On Wed, 22 Mar 2023 11:11:09 +0000 Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote:
> > 
> > > unshare copies data from source to destination. But if the source is
> > > HOLE or UNWRITTEN extents, we should zero the destination, otherwise the
> > > result will be unexpectable.
> > 
> > Please provide much more detail on the user-visible effects of the bug.
> > For example, are we leaking kernel memory contents to userspace?
> 
> This fixes fail of generic/649.

Please make a note of easy(ish) reproducers when you know about them,
e.g.

"Found by running generic/649 while mounting with -o dax=always on
pmem."

So that anyone scanning around for fix backports has an easier time
doing an A/B comparison to assess whether or not they need the fix.
Especially if there's any chance that person is you circa 2024. ;)

--D

> 
> --
> Thanks,
> Ruan.
> 
> > 
> > Thanks.
> > 
> >