linux-kernel - [Linux-kernel-mentees] [PATCH v2] usbhid: Fix slab-out-of-bounds write in hiddev_ioctl

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Date:   Mon, 20 Jul 2020 15:52:09 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Peilin Ye <yepeilin.cs@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        syzkaller-bugs@...glegroups.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-usb@...r.kernel.org, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [Linux-kernel-mentees] [PATCH v2] usbhid: Fix slab-out-of-bounds write in hiddev_ioctl_usage()

`uref->usage_index` is not always being properly checked, causing
hiddev_ioctl_usage() to go out of bounds under some cases. Fix it.

Reported-by: syzbot+34ee1b45d88571c2fa8b@...kaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=f2aebe90b8c56806b050a20b36f51ed6acabe802
Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
---
Change in v2:
    - Add the same check for the `HIDIOCGUSAGE` case. (Suggested by
      Dan Carpenter <dan.carpenter@...cle.com>)

 drivers/hid/usbhid/hiddev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 4140dea693e9..4f97e6c12059 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -519,12 +519,16 @@ static noinline int hiddev_ioctl_usage(struct hiddev *hiddev, unsigned int cmd,
 
 		switch (cmd) {
 		case HIDIOCGUSAGE:
+			if (uref->usage_index >= field->report_count)
+				goto inval;
 			uref->value = field->value[uref->usage_index];
 			if (copy_to_user(user_arg, uref, sizeof(*uref)))
 				goto fault;
 			goto goodreturn;
 
 		case HIDIOCSUSAGE:
+			if (uref->usage_index >= field->report_count)
+				goto inval;
 			field->value[uref->usage_index] = uref->value;
 			goto goodreturn;
 
-- 
2.25.1