linux-kernel - Re: [PATCH v6 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields

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Message-Id: <20190417150202.b7cec444cf81ed44a150ea9d@linux-foundation.org>
Date:   Wed, 17 Apr 2019 15:02:02 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     stable@...r.kernel.org, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        mhocko@...e.com, david@...hat.com
Subject: Re: [PATCH v6 11/12] libnvdimm/pfn: Fix fsdax-mode namespace
 info-block zero-fields

On Wed, 17 Apr 2019 11:39:52 -0700 Dan Williams <dan.j.williams@...el.com> wrote:

> At namespace creation time there is the potential for the "expected to
> be zero" fields of a 'pfn' info-block to be filled with indeterminate
> data. While the kernel buffer is zeroed on allocation it is immediately
> overwritten by nd_pfn_validate() filling it with the current contents of
> the on-media info-block location. For fields like, 'flags' and the
> 'padding' it potentially means that future implementations can not rely
> on those fields being zero.
> 
> In preparation to stop using the 'start_pad' and 'end_trunc' fields for
> section alignment, arrange for fields that are not explicitly
> initialized to be guaranteed zero. Bump the minor version to indicate it
> is safe to assume the 'padding' and 'flags' are zero. Otherwise, this
> corruption is expected to benign since all other critical fields are
> explicitly initialized.
> 
> Fixes: 32ab0a3f5170 ("libnvdimm, pmem: 'struct page' for pmem")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Buried at the end of a 12 patch series.  Should this be a standalone
patch, suitable for a prompt merge?