On Thu, Sep 17, 2020 at 02:03:11PM +0200, Oliver Neukum wrote:
> Am Donnerstag, den 17.09.2020, 13:43 +0200 schrieb Greg KH:
> > On Thu, Sep 17, 2020 at 12:34:27PM +0200, Oliver Neukum wrote:
> > > read() needs to check whether the device has been
> > > disconnected before it tries to talk to the device.
> > >
> > > Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
> > > Reported-by: syzbot+be5b5f86a162a6c281e6@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > ---
> > > drivers/usb/class/usblp.c | 5 +++++
> > > 1 file changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/usb/class/usblp.c b/drivers/usb/class/usblp.c
> > > index 084c48c5848f..67cbd42421be 100644
> > > --- a/drivers/usb/class/usblp.c
> > > +++ b/drivers/usb/class/usblp.c
> > > @@ -827,6 +827,11 @@ static ssize_t usblp_read(struct file *file, char __user *buffer, size_t len, lo
> > > if (rv < 0)
> > > return rv;
> > >
> > > + if (!usblp->present) {
> > > + count = -ENODEV;
> > > + goto done;
> > > + }
> > > +
> >
> > What prevents ->present from not being changed right after this test?
>
> Hi,
>
> the mutex taken in
>
> rv = usblp_rwait_and_lock(usblp, !!(file->f_flags & O_NONBLOCK));
Ah, missed that, thanks.
greg k-h
