| Message ID | 155552639290.2015392.17304211251966796338.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | mm: Sub-section memory hotplug support | expand |
On Wed, 17 Apr 2019 11:39:52 -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> Buried at the end of a 12 patch series. Should this be a standalone patch, suitable for a prompt merge?
On Wed, Apr 17, 2019 at 3:02 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Wed, 17 Apr 2019 11:39:52 -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> > > 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 indeed initialized.
diff --git a/drivers/nvdimm/dax_devs.c b/drivers/nvdimm/dax_devs.c index 0453f49dc708..326f02ffca81 100644 --- a/drivers/nvdimm/dax_devs.c +++ b/drivers/nvdimm/dax_devs.c @@ -126,7 +126,7 @@ int nd_dax_probe(struct device *dev, struct nd_namespace_common *ndns) 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>"); diff --git a/drivers/nvdimm/pfn.h b/drivers/nvdimm/pfn.h index dde9853453d3..e901e3a3b04c 100644 --- a/drivers/nvdimm/pfn.h +++ b/drivers/nvdimm/pfn.h @@ -36,6 +36,7 @@ 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; }; diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c index 01f40672507f..a2406253eb70 100644 --- a/drivers/nvdimm/pfn_devs.c +++ b/drivers/nvdimm/pfn_devs.c @@ -420,6 +420,15 @@ static int nd_pfn_clear_memmap_errors(struct nd_pfn *nd_pfn) 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; @@ -565,7 +574,7 @@ int nd_pfn_probe(struct device *dev, struct nd_namespace_common *ndns) 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); @@ -702,7 +711,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) 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; @@ -711,11 +720,14 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) 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, @@ -768,7 +780,7 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn) 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);
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> --- drivers/nvdimm/dax_devs.c | 2 +- drivers/nvdimm/pfn.h | 1 + drivers/nvdimm/pfn_devs.c | 18 +++++++++++++++--- 3 files changed, 17 insertions(+), 4 deletions(-)