[alsa-devel] [PATCH 2/3] ucm: add a FIXME comment

[Tanu Kaskinen]

On Wed, 2015-02-11 at 12:38 +0100, Takashi Iwai wrote:
> At Tue, 10 Feb 2015 22:42:33 +0200,
> Tanu Kaskinen wrote:
> > 
> > I'm pretty sure the current code will crash with some inputs, but I
> > don't know what the original author intended this code to do, so I
> > don't know how to fix it.
> > ---
> >  src/ucm/main.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/src/ucm/main.c b/src/ucm/main.c
> > index 3924aee..62bc374 100644
> > --- a/src/ucm/main.c
> > +++ b/src/ucm/main.c
> > @@ -317,6 +317,14 @@ static int execute_sequence(snd_use_case_mgr_t *uc_mgr,
> >  					uc_error("cdev is not defined!");
> >  					return err;
> >  				}
> > +                                /* FIXME: If cdev1 is NULL and cdev2 is not,
> > +                                 * then set cdev to cdev1... makes no sense!
> > +                                 * Also, what if both cdev1 and cdev2 are NULL?
> > +                                 * What should happen? Later in this function we
> > +                                 * call open_ctl(), which assumes non-NULL cdev,
> > +                                 * so leaving cdev to NULL here is not an
> > +                                 * option (or at least cdev has to be checked
> > +                                 * before calling open_ctl()). */
> >  				if (cdev1 == NULL || cdev2 == NULL ||
> >                                      strcmp(cdev1, cdev2) == 0) {
> >  					cdev = (char *)cdev1;
> 
> Ouch, the code is really buggy there.  We must fix it instead of
> leaving FIXME.
> 
> I see there are multiple bugs (in addition to your patch#1):
> 
> - the error check is wrong, it should be compared with -ENOENT
> 	if (err < 0 && err != ENOENT)
> 
>   This leaves cdev1 or cdev2 NULL as non-error.
> 
> - The intention of the code should be (as far as I understand):
>   - if only one of cdev1 and cdev2 is defined, take it as cdev
>   - if cdev1 and cdev2 are defined and have the same string, keep
>     cdev1 and free cdev2
>   - in the rest cases, free both cdev1 and cdev2 without changing cdev

Regarding that last case, just leaving cdev unchanged is not a good
idea. cdev will always be NULL if we don't set it here, and when we call
open_ctl(), it must be non-NULL.

-- 
Tanu