[PATCH] usbhid: fix info leak in hid_submit_ctrl

[Benjamin Tissoires]

On Wed, May 5, 2021 at 2:42 PM Jiri Kosina <jikos at 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 at syzkaller.appspotmail.com
> > Signed-off-by: Anirudh Rayabharam <mail at 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