From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 7 Jun 2019 12:54:30 -0700 From: Andrew Morton Subject: Re: [PATCH v9 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields Message-Id: <20190607125430.81e63cd56590ab3fea37a635@linux-foundation.org> In-Reply-To: References: <155977186863.2443951.9036044808311959913.stgit@dwillia2-desk3.amr.corp.intel.com> <155977193862.2443951.10284714500308539570.stgit@dwillia2-desk3.amr.corp.intel.com> <20190606144643.4f3363db9499ebbf8f76e62e@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Dan Williams Cc: stable , Linux MM , linux-nvdimm , Linux Kernel Mailing List , Oscar Salvador , Michal Hocko List-ID: On Thu, 6 Jun 2019 15:06:26 -0700 Dan Williams wrote: > On Thu, Jun 6, 2019 at 2:46 PM Andrew Morton wrote: > > > > On Wed, 05 Jun 2019 14:58:58 -0700 Dan Williams 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: > > > Signed-off-by: Dan Williams > > > > 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?