From 6be388f4a35d2ce5ef7dbf635a8964a5da7f799f Mon Sep 17 00:00:00 2001
From: Anirudh Rayabharam <mail@anirudhrb.com>
Date: Sun, 25 Apr 2021 23:03:53 +0530
Subject: [PATCH] HID: usbhid: fix info leak in hid_submit_ctrl
Git-commit: 6be388f4a35d2ce5ef7dbf635a8964a5da7f799f
Patch-mainline: v5.13-rc5
References: git-fixes

In hid_submit_ctrl(), the way of calculating the report length doesn't
take into account that report->size can be zero. When running the
syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to
calculate transfer_buffer_length as 16384. When this urb is passed to
the usb core layer, KMSAN reports an info leak of 16384 bytes.

To fix this, first modify hid_report_len() to account for the zero
report size case by using DIV_ROUND_UP for the division. Then, call it
from hid_submit_ctrl().

Reported-by: syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/hid/usbhid/hid-core.c |    2 +-
 include/linux/hid.h           |    3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -375,7 +375,7 @@ static int hid_submit_ctrl(struct hid_de
 	raw_report = usbhid->ctrl[usbhid->ctrltail].raw_report;
 	dir = usbhid->ctrl[usbhid->ctrltail].dir;
 
-	len = ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	len = hid_report_len(report);
 	if (dir == USB_DIR_OUT) {
 		usbhid->urbctrl->pipe = usb_sndctrlpipe(hid_to_usb_dev(hid), 0);
 		usbhid->urbctrl->transfer_buffer_length = len;
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1133,8 +1133,7 @@ static inline void hid_hw_wait(struct hi
  */
 static inline int hid_report_len(struct hid_report *report)
 {
-	/* equivalent to DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) */
-	return ((report->size - 1) >> 3) + 1 + (report->id > 0);
+	return DIV_ROUND_UP(report->size, 8) + (report->id > 0);
 }
 
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, int size,