On Mon, Mar 2, 2020 at 4:09 AM Aneesh Kumar K.V
[off-list ref] wrote:

Dan Williams [off-list ref] writes:

quoted

The pmem driver on PowerPC crashes with the following signature when
instantiating misaligned namespaces that map their capacity via
memremap_pages().

    BUG: Unable to handle kernel data access at 0xc001000406000000
    Faulting instruction address: 0xc000000000090790
    NIP [c000000000090790] arch_add_memory+0xc0/0x130
    LR [c000000000090744] arch_add_memory+0x74/0x130
    Call Trace:
     arch_add_memory+0x74/0x130 (unreliable)
     memremap_pages+0x74c/0xa30
     devm_memremap_pages+0x3c/0xa0
     pmem_attach_disk+0x188/0x770
     nvdimm_bus_probe+0xd8/0x470

With the assumption that only memremap_pages() has alignment
constraints, enforce memremap_compat_align() for
pmem_should_map_pages(), nd_pfn, and nd_dax cases. This includes
preventing the creation of namespaces where the base address is
misaligned and cases there infoblock padding parameters are invalid.

Reviewed-by: Aneesh Kumar K.V <redacted>

quoted

Reported-by: Aneesh Kumar K.V <redacted>
Cc: Jeff Moyer <redacted>
Fixes: a3619190d62e ("libnvdimm/pfn: stop padding pmem namespaces to section alignment")
Signed-off-by: Dan Williams <redacted>
---
 drivers/nvdimm/namespace_devs.c |   12 ++++++++++++
 drivers/nvdimm/pfn_devs.c       |   26 +++++++++++++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 032dc61725ff..68e89855f779 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c

@@ -10,6 +10,7 @@
 #include <linux/nd.h>
 #include "nd-core.h"
 #include "pmem.h"
+#include "pfn.h"
 #include "nd.h"

 static void namespace_io_release(struct device *dev)

@@ -1739,6 +1740,17 @@ struct nd_namespace_common *nvdimm_namespace_common_probe(struct device *dev)
              return ERR_PTR(-ENODEV);
      }

May be add a comment here that both dax/fsdax namespace details are
checked in nd_pfn_validate() so that we look at start_pad and end_trunc
while validating the namespace?

quoted

+     if (pmem_should_map_pages(dev)) {
+             struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
+             struct resource *res = &nsio->res;
+
+             if (!IS_ALIGNED(res->start | (res->end + 1),
+                                     memremap_compat_align())) {
+                     dev_err(&ndns->dev, "%pr misaligned, unable to map\n", res);
+                     return ERR_PTR(-EOPNOTSUPP);
+             }
+     }
+
      if (is_namespace_pmem(&ndns->dev)) {
              struct nd_namespace_pmem *nspm;

diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 79fe02d6f657..3bdd4b883d05 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c

@@ -446,6 +446,7 @@ static bool nd_supported_alignment(unsigned long align)
 int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 {
      u64 checksum, offset;
+     struct resource *res;
      enum nd_pfn_mode mode;
      struct nd_namespace_io *nsio;
      unsigned long align, start_pad;

@@ -578,13 +579,14 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
       * established.
       */
      nsio = to_nd_namespace_io(&ndns->dev);
-     if (offset >= resource_size(&nsio->res)) {
+     res = &nsio->res;
+     if (offset >= resource_size(res)) {
              dev_err(&nd_pfn->dev, "pfn array size exceeds capacity of %s\n",
                              dev_name(&ndns->dev));
              return -EOPNOTSUPP;
      }

-     if ((align && !IS_ALIGNED(nsio->res.start + offset + start_pad, align))
+     if ((align && !IS_ALIGNED(res->start + offset + start_pad, align))
                      || !IS_ALIGNED(offset, PAGE_SIZE)) {
              dev_err(&nd_pfn->dev,
                              "bad offset: %#llx dax disabled align: %#lx\n",

@@ -592,6 +594,18 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
              return -EOPNOTSUPP;
      }

+     if (!IS_ALIGNED(res->start + le32_to_cpu(pfn_sb->start_pad),
+                             memremap_compat_align())) {
+             dev_err(&nd_pfn->dev, "resource start misaligned\n");
+             return -EOPNOTSUPP;
+     }
+
+     if (!IS_ALIGNED(res->end + 1 - le32_to_cpu(pfn_sb->end_trunc),
+                             memremap_compat_align())) {
+             dev_err(&nd_pfn->dev, "resource end misaligned\n");
+             return -EOPNOTSUPP;
+     }
+
      return 0;
 }
 EXPORT_SYMBOL(nd_pfn_validate);

@@ -750,7 +764,13 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
      start = nsio->res.start;
      size = resource_size(&nsio->res);
      npfns = PHYS_PFN(size - SZ_8K);
-     align = max(nd_pfn->align, SUBSECTION_SIZE);
+     align = max(nd_pfn->align, memremap_compat_align());
+     if (!IS_ALIGNED(start, memremap_compat_align())) {
+             dev_err(&nd_pfn->dev, "%s: start %pa misaligned to %#lx\n",
+                             dev_name(&ndns->dev), &start,
+                             memremap_compat_align());
+             return -EINVAL;
+     }

This validates start in case of a new namespace creation where the user
updated nd_region->align value? A comment there would help when looking
at the code later?

Yeah, sounds good will respin with those updates.