Re: [PATCH 1/1] HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT related user initiated OOB write

[Lee Jones <lee@kernel.org>]

On Tue, 17 Mar 2026, Benjamin Tissoires wrote:

> On Mar 17 2026, Lee Jones wrote:
> > logi_dj_recv_send_report() assumes that all incoming REPORT_ID_DJ_SHORT
> > reports are 14 Bytes (DJREPORT_SHORT_LENGTH - 1) long.  It uses that
> > assumption to load the associated field's 'value' array with 14 Bytes of
> > data.  However, if a malicious user only sends say 1 Byte of data,
> > 'report_count' will be 1 and only 1 Byte of memory will be allocated to
> > the 'value' Byte array.  When we come to populate 'value[1-13]' we will
> > experience an OOB write.
> > 
> > Signed-off-by: Lee Jones <lee@kernel.org>
> > ---
> >  drivers/hid/hid-logitech-dj.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c
> > index 44b716697510..885b986c7a12 100644
> > --- a/drivers/hid/hid-logitech-dj.c
> > +++ b/drivers/hid/hid-logitech-dj.c
> > @@ -1282,6 +1282,12 @@ static int logi_dj_recv_send_report(struct dj_receiver_dev *djrcv_dev,
> >  		return -ENODEV;
> >  	}
> >  
> > +	if (report->maxfield < 1 || report->field[0]->report_count != DJREPORT_SHORT_LENGTH - 1) {
> 
> This is all static information. So this should be checked in the
> .probe(), once the device has been parsed, not for every single call of
> logi_dj_recv_send_report().

Doesn't report_count come from the device?

I can manipulate it with my user app.

-- 
Lee Jones [李琼斯]