[PATCH] libnvdimm: fix NULL pointer dereference

[Gustavo A. R. Silva]

ndd is being dereferenced before it is null checked, hence there is a
potential null pointer dereference.

Fix this by moving the pointer dereference after ndd has been properly
null checked at line 554: if (!ndd)

Addresses-Coverity-ID: 1472020 ("Dereference before null check")
Fixes: 42218e643bd2 ("libnvdimm: Use max contiguous area for namespace size")
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
---
 drivers/nvdimm/dimm_devs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 9e977cb..1dc3125 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -546,7 +546,7 @@ resource_size_t nd_pmem_max_contiguous_dpa(struct nd_region *nd_region,
 					   struct nd_mapping *nd_mapping)
 {
 	struct nvdimm_drvdata *ndd = to_ndd(nd_mapping);
-	struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
+	struct nvdimm_bus *nvdimm_bus;
 	resource_size_t max = 0;
 	struct resource *res;
 
@@ -554,6 +554,8 @@ resource_size_t nd_pmem_max_contiguous_dpa(struct nd_region *nd_region,
 	if (!ndd)
 		return 0;
 
+	nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
+
 	if (reserve_free_pmem(nvdimm_bus, nd_mapping))
 		return 0;
 	for_each_dpa_resource(ndd, res) {
-- 
2.7.4