[PATCH] platform/x86: acer-wmi: validate ACPI object type in acer_gsensor_event()

[Tristan Madani <tristmd@gmail.com>]

From: Tristan Madani <tristan@talencesecurity.com>

acer_gsensor_event() accesses the ACPI evaluation result as a package
without first verifying the object type.  If the firmware returns a
non-package type, the code reads package.count and package.elements
from the wrong union member, which can cause a NULL pointer
dereference or read from an invalid address.

Add a type check for ACPI_TYPE_PACKAGE before accessing the package
fields, and validate that each element is ACPI_TYPE_INTEGER before
reading integer.value.

Fixes: 1eb3fe1d3b6b ("ACER: Add support for accelerometer sensor")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
 drivers/platform/x86/acer-wmi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index 61ae622c93d94..72b44f02a992f 100644
--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -2043,7 +2043,12 @@ static int acer_gsensor_event(void)
 	if (ACPI_FAILURE(status))
 		return -1;
 
-	if (out_obj->package.count != 4)
+	if (out_obj->type != ACPI_TYPE_PACKAGE || out_obj->package.count != 4)
+		return -1;
+
+	if (out_obj->package.elements[0].type != ACPI_TYPE_INTEGER ||
+	    out_obj->package.elements[1].type != ACPI_TYPE_INTEGER ||
+	    out_obj->package.elements[2].type != ACPI_TYPE_INTEGER)
 		return -1;
 
 	input_report_abs(acer_wmi_accel_dev, ABS_X,
-- 
2.47.3