oss-security - Linux Kernel: hid: NULL pointer dereference in hid_betopff

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Date: Wed, 18 Jan 2023 16:20:51 +0100
From: Pietro Borrello <borrello@...g.uniroma1.it>
To: oss-security@...ts.openwall.com
Subject: Linux Kernel: hid: NULL pointer dereference in hid_betopff_play()

Hi all,

I'm disclosing a possible DoS when plugging in a malicious USB device,
which advertises itself as a betop USB device.

A device driver must check that the device correctly registered the
expected inputs and reports.
Otherwise, a malicious USB device may violate assumptions throughout
the driver's code.

betopff_init() in the betop driver's code only checks that the device advertises
at least 4 report values among all its fields, but hid_betopff_play() expects
at least 4 report fields with a value each.
A device advertising an output report with one field and 4 report values
would pass the check but crash the kernel with a NULL pointer dereference
in hid_betopff_play(), when accessing `betopff->report->field[2]->value[0]`.

Best regards,
Pietro Borrello

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