Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210425173353.10231-1-mail@anirudhrb.com> <nycvar.YFH.7.76.2105051442120.28378@cbobk.fhfr.pm>
In-Reply-To: <nycvar.YFH.7.76.2105051442120.28378@cbobk.fhfr.pm>
From:   Benjamin Tissoires <benjamin.tissoires@redhat.com>
Date:   Wed, 5 May 2021 15:25:30 +0200
Message-ID: <CAO-hwJJ4u5NZ-81Tq3PGu-F9r3iUSCiKp=JUsTfuVsyd-Sxsew@mail.gmail.com>
Subject: Re: [PATCH] usbhid: fix info leak in hid_submit_ctrl
To:     Jiri Kosina <jikos@kernel.org>
Cc:     Anirudh Rayabharam <mail@anirudhrb.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel-mentees@lists.linuxfoundation.org,
        syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com,
        Linux USB Mailing List <linux-usb@vger.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, May 5, 2021 at 2:42 PM Jiri Kosina <jikos@kernel.org> wrote:
>
> On Sun, 25 Apr 2021, Anirudh Rayabharam wrote:
>
> > 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>
>
> Benjamin, could you please run this one through your regression testing
> machinery before we send it upstream?
>

I don't have a reproducer like syzbot has for the exact bug here, as I
am relying on one real USB device to check if usbhid is not too
broken.
However, the test suite should catch if there is an error implied by
the hid_report_len() change.

Anyway, I manually started the job and will report when it is done.

Cheers,
Benjamin