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    Subject[PATCH 5.2 377/413] libnvdimm/pfn: fix fsdax-mode namespace info-block zero-fields
    Date
    From: Dan Williams <dan.j.williams@intel.com>

    commit 7e3e888dfc138089f4c15a81b418e88f0978f744 upstream.

    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.

    Note The cc: stable is about spreading this new policy to as many
    kernels as possible not fixing an issue in those kernels. It is not
    until the change titled "libnvdimm/pfn: Stop padding pmem namespaces to
    section alignment" where this improper initialization becomes a problem.
    So if someone decides to backport "libnvdimm/pfn: Stop padding pmem
    namespaces to section alignment" (which is not tagged for stable), make
    sure this pre-requisite is flagged.

    Link: http://lkml.kernel.org/r/156092356065.979959.6681003754765958296.stgit@dwillia2-desk3.amr.corp.intel.com
    Fixes: 32ab0a3f5170 ("libnvdimm, pmem: 'struct page' for pmem")
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>
    Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> [ppc64]
    Cc: <stable@vger.kernel.org>
    Cc: David Hildenbrand <david@redhat.com>
    Cc: Jane Chu <jane.chu@oracle.com>
    Cc: Jeff Moyer <jmoyer@redhat.com>
    Cc: Jérôme Glisse <jglisse@redhat.com>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Logan Gunthorpe <logang@deltatee.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Mike Rapoport <rppt@linux.ibm.com>
    Cc: Oscar Salvador <osalvador@suse.de>
    Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
    Cc: Toshi Kani <toshi.kani@hpe.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Wei Yang <richardw.yang@linux.intel.com>
    Cc: Jason Gunthorpe <jgg@mellanox.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/nvdimm/dax_devs.c | 2 +-
    drivers/nvdimm/pfn.h | 1 +
    drivers/nvdimm/pfn_devs.c | 18 +++++++++++++++---
    3 files changed, 17 insertions(+), 4 deletions(-)

    --- a/drivers/nvdimm/dax_devs.c
    +++ b/drivers/nvdimm/dax_devs.c
    @@ -118,7 +118,7 @@ int nd_dax_probe(struct device *dev, str
    nvdimm_bus_unlock(&ndns->dev);
    if (!dax_dev)
    return -ENOMEM;
    - pfn_sb = devm_kzalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
    + pfn_sb = devm_kmalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
    nd_pfn->pfn_sb = pfn_sb;
    rc = nd_pfn_validate(nd_pfn, DAX_SIG);
    dev_dbg(dev, "dax: %s\n", rc == 0 ? dev_name(dax_dev) : "<none>");
    --- a/drivers/nvdimm/pfn.h
    +++ b/drivers/nvdimm/pfn.h
    @@ -28,6 +28,7 @@ struct nd_pfn_sb {
    __le32 end_trunc;
    /* minor-version-2 record the base alignment of the mapping */
    __le32 align;
    + /* minor-version-3 guarantee the padding and flags are zero */
    u8 padding[4000];
    __le64 checksum;
    };
    --- a/drivers/nvdimm/pfn_devs.c
    +++ b/drivers/nvdimm/pfn_devs.c
    @@ -412,6 +412,15 @@ static int nd_pfn_clear_memmap_errors(st
    return 0;
    }

    +/**
    + * nd_pfn_validate - read and validate info-block
    + * @nd_pfn: fsdax namespace runtime state / properties
    + * @sig: 'devdax' or 'fsdax' signature
    + *
    + * Upon return the info-block buffer contents (->pfn_sb) are
    + * indeterminate when validation fails, and a coherent info-block
    + * otherwise.
    + */
    int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
    {
    u64 checksum, offset;
    @@ -557,7 +566,7 @@ int nd_pfn_probe(struct device *dev, str
    nvdimm_bus_unlock(&ndns->dev);
    if (!pfn_dev)
    return -ENOMEM;
    - pfn_sb = devm_kzalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
    + pfn_sb = devm_kmalloc(dev, sizeof(*pfn_sb), GFP_KERNEL);
    nd_pfn = to_nd_pfn(pfn_dev);
    nd_pfn->pfn_sb = pfn_sb;
    rc = nd_pfn_validate(nd_pfn, PFN_SIG);
    @@ -694,7 +703,7 @@ static int nd_pfn_init(struct nd_pfn *nd
    u64 checksum;
    int rc;

    - pfn_sb = devm_kzalloc(&nd_pfn->dev, sizeof(*pfn_sb), GFP_KERNEL);
    + pfn_sb = devm_kmalloc(&nd_pfn->dev, sizeof(*pfn_sb), GFP_KERNEL);
    if (!pfn_sb)
    return -ENOMEM;

    @@ -703,11 +712,14 @@ static int nd_pfn_init(struct nd_pfn *nd
    sig = DAX_SIG;
    else
    sig = PFN_SIG;
    +
    rc = nd_pfn_validate(nd_pfn, sig);
    if (rc != -ENODEV)
    return rc;

    /* no info block, do init */;
    + memset(pfn_sb, 0, sizeof(*pfn_sb));
    +
    nd_region = to_nd_region(nd_pfn->dev.parent);
    if (nd_region->ro) {
    dev_info(&nd_pfn->dev,
    @@ -760,7 +772,7 @@ static int nd_pfn_init(struct nd_pfn *nd
    memcpy(pfn_sb->uuid, nd_pfn->uuid, 16);
    memcpy(pfn_sb->parent_uuid, nd_dev_to_uuid(&ndns->dev), 16);
    pfn_sb->version_major = cpu_to_le16(1);
    - pfn_sb->version_minor = cpu_to_le16(2);
    + pfn_sb->version_minor = cpu_to_le16(3);
    pfn_sb->start_pad = cpu_to_le32(start_pad);
    pfn_sb->end_trunc = cpu_to_le32(end_trunc);
    pfn_sb->align = cpu_to_le32(nd_pfn->align);

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