[PATCH v3 2/5] ACPI / bus: Do not traverse through non-existed device table

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

When __acpi_match_device() is called it would be possible to have
ACPI ID table a MULL pointer. To avoid potential dereference,
check for this before traverse.

While here, remove redundant 'else'.

Cc: Sinan Kaya <okaya@codeaurora.org>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/acpi/bus.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 761286e50067..da7e9cf770a6 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -752,11 +752,13 @@ static const struct acpi_device_id *__acpi_match_device(
 
 	list_for_each_entry(hwid, &device->pnp.ids, list) {
 		/* First, check the ACPI/PNP IDs provided by the caller. */
-		for (id = ids; id->id[0] || id->cls; id++) {
-			if (id->id[0] && !strcmp((char *) id->id, hwid->id))
-				return id;
-			else if (id->cls && __acpi_match_device_cls(id, hwid))
-				return id;
+		if (ids) {
+			for (id = ids; id->id[0] || id->cls; id++) {
+				if (id->id[0] && !strcmp((char *)id->id, hwid->id))
+					return id;
+				if (id->cls && __acpi_match_device_cls(id, hwid))
+					return id;
+			}
 		}
 
 		/*
-- 
2.15.1