Re: [PATCH] jsm_tty: Fix a possible null pointer dereference in two functions

[Joe Perches <joe@perches.com>]

On Wed, 2017-11-29 at 18:05 +0000, Greg Kroah-Hartman wrote:
> On Wed, Nov 29, 2017 at 09:51:36AM -0800, Joe Perches wrote:
> > On Wed, 2017-11-29 at 17:35 +0000, Greg Kroah-Hartman wrote:
> > > On Wed, Nov 29, 2017 at 09:23:07AM -0800, Joe Perches wrote:
> > > > On Wed, 2017-11-29 at 17:40 +0100, SF Markus Elfring wrote:
> > > > > From: Markus Elfring <elfring@users.sourceforge.net>
> > > > > Date: Wed, 29 Nov 2017 17:30:36 +0100
> > > > > 
> > > > > Move two debug messages so that a null pointer access can not happen
> > > > > for the variable "ch" in these functions.
> > > > 
> > > > An actual defect fix!
> > > 
> > > Nope, not at all, this does not "fix" anything.
> > 
> > Well, I believe it does in unusual cases like a
> > CONFIG_DYNAMIC_DEBUG when this is enabled by an
> > odd +p in the dynamic debug control file.
> > 
> > > > Here you could probably cc stable too.
> > > 
> > > Nope, not worth it.
> > 
> > <shrug>
> > 
> > It's pretty unlikely, but it is an actual defect.
> 
> No it is not, those variables will never be set to NULL, so this can
> never be triggered.  Walk up the call chain.

Right you are.  Local analysis isn't enough.
The code could/should be removed, but it's not a defect.

cheers, Joe