Re: [PATCH 1/3] thermal: testing: Avoid NULL pointer dereference on missing arg

[David Laight]

On Sat, 6 Jun 2026 19:52:49 -0700
Guru Das Srinagesh <linux@xxxxxxxxxxx> wrote:

> On Sun, Jun 07, 2026 at 12:04:18AM +0300, Ovidiu Panait wrote:
> [...]
> > To fix this, make arg an empty string instead of leaving it NULL when the
> > separator is missing. sscanf() then fails correctly with -EINVAL on it.  
> [...]
> > ---
> >  drivers/thermal/testing/command.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/thermal/testing/command.c b/drivers/thermal/testing/command.c
> > index 1159ecea57e7..5513a26feed7 100644
> > --- a/drivers/thermal/testing/command.c
> > +++ b/drivers/thermal/testing/command.c
> > @@ -150,6 +150,8 @@ static ssize_t tt_command_process(char *s)
> >  	if (arg) {
> >  		*arg = '\0';
> >  		arg++;
> > +	} else {
> > +		arg = s + strlen(s);
> >  	}  
> 
> Here, `arg` is made to point to the NUL terminator of s. Couldn't this be simplified to:
> 
> 	arg = "";
> 
> to make the intent clearer? Since `tt_command_exec()` takes in arg as `const char *`,
> pointing `arg` to a string literal is fine.
> 

Except that 'arg' itself must be 'char *' otherwise the '*arg = 0'
higher up will fail.

So you'd need to handle it differently.

-- David