Re: potential-null-pointer-dereference-in-amiga-serial-driver.patch added to -mm tree

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Wed, Jun 01, 2005 at 10:21:08PM -0700, Greg KH wrote:
> On Tue, May 31, 2005 at 09:22:15AM -0300, Marcelo Tosatti wrote:
> > 
> > Hi Alexey,
> > 
> > On Tue, May 31, 2005 at 07:49:15PM +0400, Alexey Dobriyan wrote:
> > > On Tuesday 31 May 2005 13:08, akpm@osdl.org wrote:
> > > > A pointer is dereferenced before it is null-checked.
> > > 
> > > > --- 25/drivers/char/amiserial.c~potential-null-pointer-dereference-in-amiga-serial-driver
> > > > +++ 25-akpm/drivers/char/amiserial.c
> > > 
> > > >  static void rs_put_char(struct tty_struct *tty, unsigned char ch)
> > > >  {
> > > > -	struct async_struct *info = (struct async_struct *)tty->driver_data;
> > > > +	struct async_struct *info;
> > > >  	unsigned long flags;
> > > >  
> > > > +	if (!tty)
> > > > +		return;
> > > 
> > > Can ->put_char be ever called with tty being NULL? From my reading of
> > > drivers/char/n_tty.c it can't.
> > 
> > Nope it can't, but the change makes the code more readable IMO, while handling
> > a NULL "tty" argument properly (which the old version pretends to, but doesnt).
> 
> But unneeded checks like this are not encouraged in the kernel.  As the
> tty pointer can never be null, don't worry about it.

OK - so better just remove the check. Julien, care to follow Greg's 
recommendation and refresh the patch?