libnvdimm: Fix dereference of pointer ndns before it is null checked

Commit Message

Jing Xiangfeng Sept. 15, 2020, 7:06 a.m. UTC

In current code, the pointer ndns is being dereferenced on the
initialization of pointer parent_uuid before ndns is null check. This
could lead to a potential null pointer dereference. Fix this by
dereferencing ndns after ndns has been null pointer sanity checked.

Signed-off-by: Jing Xiangfeng <[e-mail]>
---
 drivers/nvdimm/pfn_devs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 3e11ef8d3f5b..c443994f81f3 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -452,7 +452,7 @@  int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 	unsigned long align, start_pad;
 	struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
 	struct nd_namespace_common *ndns = nd_pfn->ndns;
-	const u8 *parent_uuid = nd_dev_to_uuid(&ndns->dev);
+	const u8 *parent_uuid;
 
 	if (!pfn_sb || !ndns)
 		return -ENODEV;
@@ -472,6 +472,7 @@  int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 		return -ENODEV;
 	pfn_sb->checksum = cpu_to_le64(checksum);
 
+	parent_uuid = nd_dev_to_uuid(&ndns->dev);
 	if (memcmp(pfn_sb->parent_uuid, parent_uuid, 16) != 0)
 		return -ENODEV;