nfit: fix unchecked dereference in acpi_nfit_ctl

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@intel.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index b8040fed2a69..7c479002e798 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -408,7 +408,8 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
         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_descriptor *nd_desc, struct nvdimm *nvdimm,
                  * 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;
         }