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From:   Mario Limonciello <mario.limonciello@dell.com>
To:     Hans De Goede <hdegoede@redhat.com>,
        Mark Gross <mgross@linux.intel.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        platform-driver-x86@vger.kernel.org,
        Mario Limonciello <mario.limonciello@dell.com>
Subject: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference
Date:   Fri, 29 Jan 2021 11:26:54 -0600
Message-Id: <20210129172654.2326751-1-mario.limonciello@dell.com>
MIME-Version: 1.0
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An upcoming Dell platform is causing a NULL pointer dereference
in dell-wmi-sysman initialization.  Validate that the input from
BIOS matches correct ACPI types and abort module initialization
if it fails.

This leads to a memory leak that needs to be cleaned up properly.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
---
 drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell-wmi-sysman/sysman.c
index dc6dd531c996..38b497991071 100644
--- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
+++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
@@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const char *guid)
 		return retval;
 	/* need to use specific instance_id and guid combination to get right data */
 	obj = get_wmiobj_pointer(instance_id, guid);
-	if (!obj)
+	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
+		release_attributes_data();
 		return -ENODEV;
+	}
 	elements = obj->package.elements;
 
 	mutex_lock(&wmi_priv.mutex);
 	while (elements) {
 		/* sanity checking */
+		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
+			pr_debug("incorrect element type\n");
+			goto nextobj;
+		}
 		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
 			pr_debug("empty attribute found\n");
 			goto nextobj;
-- 
2.25.1