[PATCH 4.19 18/80] HID: check empty report_list in hid_validate_values()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Pietro Borrello <borrello@diag.uniroma1.it>

[ Upstream commit b12fece4c64857e5fab4290bf01b2e0317a88456 ]

Add a check for empty report_list in hid_validate_values().
The missing check causes a type confusion when issuing a list_entry()
on an empty report_list.
The problem is caused by the assumption that the device must
have valid report_list. While this will be true for all normal HID
devices, a suitably malicious device can violate the assumption.

Fixes: 1b15d2e5b807 ("HID: core: fix validation of report id 0")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hid/hid-core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 62656636d30c..8cc79d0d11fb 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -980,8 +980,8 @@ struct hid_report *hid_validate_values(struct hid_device *hid,
 		 * Validating on id 0 means we should examine the first
 		 * report in the list.
 		 */
-		report = list_entry(
-				hid->report_enum[type].report_list.next,
+		report = list_first_entry_or_null(
+				&hid->report_enum[type].report_list,
 				struct hid_report, list);
 	} else {
 		report = hid->report_enum[type].report_id_hash[id];
-- 
2.39.0