On Wed, Apr 17, 2019 at 3:02 PM Andrew Morton <akpm(a)linux-foundation.org> wrote:
On Wed, 17 Apr 2019 11:39:52 -0700 Dan Williams <dan.j.williams(a)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
> 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,
> corruption is expected to benign since all other critical fields are
> explicitly initialized.
> Fixes: 32ab0a3f5170 ("libnvdimm, pmem: 'struct page' for pmem")
> Cc: <stable(a)vger.kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams(a)intel.com>
Buried at the end of a 12 patch series. Should this be a standalone
patch, suitable for a prompt merge?
It's not a problem unless a kernel implementation is explicitly
expecting those fields to be zero-initialized. I only marked it for
-stable in case some future kernel backports patch12. Otherwise it's
benign on older kernels that don't have patch12 since all fields are