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From: Andrew Morton <akpm@linux-foundation.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: stable <stable@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Oscar Salvador <osalvador@suse.de>,
	Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH v9 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields
Date: Fri, 7 Jun 2019 12:54:30 -0700	[thread overview]
Message-ID: <20190607125430.81e63cd56590ab3fea37a635@linux-foundation.org> (raw)
In-Reply-To: <CAPcyv4hHs75hYs+Ye+NHHiU31C6CnBqCFdo=2c5seN7kvxKOrw@mail.gmail.com>

On Thu, 6 Jun 2019 15:06:26 -0700 Dan Williams <dan.j.williams@intel.com> wrote:

> On Thu, Jun 6, 2019 at 2:46 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Wed, 05 Jun 2019 14:58:58 -0700 Dan Williams <dan.j.williams@intel.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@vger.kernel.org>
> > > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> >
> > The cc:stable in [11/12] seems odd.  Is this independent of the other
> > patches?  If so, shouldn't it be a standalone thing which can be
> > prioritized?
> >
> 
> The cc: stable is about spreading this new policy to as many kernels
> as possible not fixing an issue in those kernels. It's not until patch
> 12 "libnvdimm/pfn: Stop padding pmem namespaces to section alignment"
> as all previous kernel do initialize all fields.
> 
> I'd be ok to drop that cc: stable, my concern is distros that somehow
> pickup and backport patch 12 and miss patch 11.

Could you please propose a changelog paragraph which explains all this
to those who will be considering this patch for backports?


  reply	other threads:[~2019-06-07 19:54 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-05 21:57 [PATCH v9 00/12] mm: Sub-section memory hotplug support Dan Williams
2019-06-05 21:57 ` [PATCH v9 01/12] mm/sparsemem: Introduce struct mem_section_usage Dan Williams
2019-06-06 17:34   ` Oscar Salvador
2019-06-16 13:11   ` Wei Yang
2019-06-18 21:56     ` Dan Williams
2019-06-19  2:13       ` Wei Yang
2019-06-05 21:57 ` [PATCH v9 02/12] mm/sparsemem: Add helpers track active portions of a section at boot Dan Williams
2019-06-06 16:55   ` Oscar Salvador
2019-06-17 22:21   ` Wei Yang
2019-06-17 22:32     ` Dan Williams
2019-06-18  1:03       ` Wei Yang
2019-06-19  3:15       ` Dan Williams
2019-06-05 21:58 ` [PATCH v9 03/12] mm/hotplug: Prepare shrink_{zone, pgdat}_span for sub-section removal Dan Williams
2019-06-18  1:42   ` Wei Yang
2019-06-19  3:40     ` Dan Williams
2019-06-05 21:58 ` [PATCH v9 04/12] mm/sparsemem: Convert kmalloc_section_memmap() to populate_section_memmap() Dan Williams
2019-06-06 17:02   ` Oscar Salvador
2019-06-16  6:06   ` Aneesh Kumar K.V
2019-06-05 21:58 ` [PATCH v9 05/12] mm/hotplug: Kill is_dev_zone() usage in __remove_pages() Dan Williams
2019-06-05 21:58 ` [PATCH v9 06/12] mm: Kill is_dev_zone() helper Dan Williams
2019-06-18  3:35   ` Wei Yang
2019-06-05 21:58 ` [PATCH v9 07/12] mm/sparsemem: Prepare for sub-section ranges Dan Williams
2019-06-06 17:21   ` Oscar Salvador
2019-06-06 18:16     ` Dan Williams
2019-06-14  8:39   ` David Hildenbrand
2019-06-05 21:58 ` [PATCH v9 08/12] mm/sparsemem: Support sub-section hotplug Dan Williams
2019-06-07  8:33   ` Oscar Salvador
2019-06-07 15:38     ` Dan Williams
2019-06-07 21:41       ` Oscar Salvador
2019-06-05 21:58 ` [PATCH v9 09/12] mm: Document ZONE_DEVICE memory-model implications Dan Williams
2019-06-05 21:58 ` [PATCH v9 10/12] mm/devm_memremap_pages: Enable sub-section remap Dan Williams
2019-06-07  8:56   ` Oscar Salvador
2019-06-16  7:49   ` Aneesh Kumar K.V
2019-06-05 21:58 ` [PATCH v9 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields Dan Williams
2019-06-06 21:46   ` Andrew Morton
2019-06-06 22:06     ` Dan Williams
2019-06-07 19:54       ` Andrew Morton [this message]
2019-06-07 20:09         ` Dan Williams
2019-06-12  9:41   ` Aneesh Kumar K.V
2019-06-05 21:59 ` [PATCH v9 12/12] libnvdimm/pfn: Stop padding pmem namespaces to section alignment Dan Williams

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