On Mon, 10 Feb 2020, Greg KH wrote:
> On Fri, Jan 31, 2020 at 08:06:52AM +0300, Dan Carpenter wrote:
> > We changed this from dev_err() to dev_WARN() in commit 0cb54a3e47cb
> > ("USB: debugging code shouldn't alter control flow").
> >
> > The difference between dev_WARN() and dev_err() is that dev_WARN()
> > prints a stack trace and if you have panic on OOPS enabled then it leads
> > to a panic. The dev_err() function just prints the error message.
> >
> > Back in the day we didn't have usb emulators fuzz testing the kernel
> > so dev_WARN() didn't cause a problem for anyone, but these days the
> > dev_WARN() interferes with syzbot so let's change this to a dev_err().
> >
> > Reported-by: syzbot+1bc2c2afd44f820a669f@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > ---
> >
> > drivers/usb/core/urb.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
> > index da923ec17612..0980c1d2253d 100644
> > --- a/drivers/usb/core/urb.c
> > +++ b/drivers/usb/core/urb.c
> > @@ -475,7 +475,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
> >
> > /* Check that the pipe's type matches the endpoint's type */
> > if (usb_urb_ep_type_check(urb))
> > - dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
> > + dev_err(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
> > usb_pipetype(urb->pipe), pipetypes[xfertype]);
>
> Like others said, we should have the stack trace here. So can you
> change this to dev_warn() and a stacktrace?
In fact we want both a stack trace and a syzbot notification, because
this particular error indicates a bug in a kernel driver. Therefore
dev_WARN is appropriate.
Alan Stern
> thanks,
>
> greg k-h
