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Subject[PATCH v2 2/4] libnvdimm/namespace: Enforce memremap_compat_align()
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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, or nd_dax cases.

Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Link: https://lore.kernel.org/r/158041477336.3889308.4581652885008605170.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/nvdimm/namespace_devs.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 032dc61725ff..aff1f32fdb4f 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -1739,6 +1739,16 @@ struct nd_namespace_common *nvdimm_namespace_common_probe(struct device *dev)
return ERR_PTR(-ENODEV);
}

+ if (pmem_should_map_pages(dev) || nd_pfn || nd_dax) {
+ struct nd_namespace_io *nsio = to_nd_namespace_io(&ndns->dev);
+ resource_size_t start = nsio->res.start;
+
+ if (!IS_ALIGNED(start | size, memremap_compat_align())) {
+ dev_dbg(&ndns->dev, "misaligned, unable to map\n");
+ return ERR_PTR(-EOPNOTSUPP);
+ }
+ }
+
if (is_namespace_pmem(&ndns->dev)) {
struct nd_namespace_pmem *nspm;

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