linux-kernel - [PATCH] fix slab-out-of-bounds in betopff

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Message-Id: <20210815083155.10559-1-asha.16@itfac.mrt.ac.lk>
Date:   Sun, 15 Aug 2021 14:01:55 +0530
From:   "F.A.Sulaiman" <asha.16@...ac.mrt.ac.lk>
To:     jikos@...nel.org, benjamin.tissoires@...hat.com
Cc:     "F.A.Sulaiman" <asha.16@...ac.mrt.ac.lk>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] fix slab-out-of-bounds in betopff_init function

This patch resolves the bug 'KASAN: slab-out-of-bounds Write in betop_probe' reported by Syzbot.

Patch resolve the bug by checking hid_device's hid_input is non empty before it's been used.

Signed-off-by: F.A. SULAIMAN <asha.16@...ac.mrt.ac.lk>
---
 drivers/hid/hid-betopff.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-betopff.c b/drivers/hid/hid-betopff.c
index 0790fbd3fc9a..6a1f894b0e97 100644
--- a/drivers/hid/hid-betopff.c
+++ b/drivers/hid/hid-betopff.c
@@ -56,19 +56,20 @@ static int betopff_init(struct hid_device *hid)
 {
 	struct betopff_device *betopff;
 	struct hid_report *report;
-	struct hid_input *hidinput =
-			list_first_entry(&hid->inputs, struct hid_input, list);
+	struct hid_input *hidinput;
 	struct list_head *report_list =
 			&hid->report_enum[HID_OUTPUT_REPORT].report_list;
-	struct input_dev *dev = hidinput->input;
+	struct input_dev *dev;
 	int field_count = 0;
 	int error;
 	int i, j;
 
-	if (list_empty(report_list)) {
+	if (list_empty(&hid->inputs)) {
 		hid_err(hid, "no output reports found\n");
 		return -ENODEV;
 	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
 
 	report = list_first_entry(report_list, struct hid_report, list);
 	/*
-- 
2.17.1