[PATCH 4.17 242/324] nfit: fix unchecked dereference in acpi_nfit_ctl

[Greg Kroah-Hartman]

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dave Jiang <dave.jiang@xxxxxxxxx>

[ Upstream commit ee6581ceba7f8314b81b2f2a81f1cf3f67c679e2 ]

Incremental patch to fix the unchecked dereference in acpi_nfit_ctl.
Reported by Dan Carpenter:

"acpi/nfit: fix cmd_rc for acpi_nfit_ctl to
always return a value" from Jun 28, 2018, leads to the following
Smatch complaint:

    drivers/acpi/nfit/core.c:578 acpi_nfit_ctl()
     warn: variable dereferenced before check 'cmd_rc' (see line 411)

drivers/acpi/nfit/core.c
   410
   411		*cmd_rc = -EINVAL;
                ^^^^^^^^^^^^^^^^^^
Patch adds unchecked dereference.

Fixes: c1985cefd844 ("acpi/nfit: fix cmd_rc for acpi_nfit_ctl to always return a value")

Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/acpi/nfit/core.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -408,7 +408,8 @@ int acpi_nfit_ctl(struct nvdimm_bus_desc
 	const guid_t *guid;
 	int rc, i;
 
-	*cmd_rc = -EINVAL;
+	if (cmd_rc)
+		*cmd_rc = -EINVAL;
 	func = cmd;
 	if (cmd == ND_CMD_CALL) {
 		call_pkg = buf;
@@ -519,7 +520,8 @@ int acpi_nfit_ctl(struct nvdimm_bus_desc
 		 * If we return an error (like elsewhere) then caller wouldn't
 		 * be able to rely upon data returned to make calculation.
 		 */
-		*cmd_rc = 0;
+		if (cmd_rc)
+			*cmd_rc = 0;
 		return 0;
 	}