[alsa-devel] [PATCH 03/14] ALSA: Add a helper to initialize device

[Takashi Iwai]

At Mon, 02 Feb 2015 14:31:40 +0100,
Lars-Peter Clausen wrote:
> 
> On 02/02/2015 11:24 AM, Takashi Iwai wrote:
> > diff --git a/sound/core/init.c b/sound/core/init.c
> > index 074875d68c15..2f730efe97b6 100644
> > --- a/sound/core/init.c
> > +++ b/sound/core/init.c
> > @@ -157,6 +157,25 @@ static int get_slot_from_bitmask(int mask, int (*check)(struct module *, int),
> >   	return mask; /* unchanged */
> >   }
> >
> > +static void default_release(struct device *dev)
> > +{
> > +}
> 
> A empty release callback is pretty much always wrong and typically causes 
> use-after-free bugs. It might be correct in this case, but there should at 
> least be a comment explaining why it is correct.

Right, a bit more explanation would be better: we have already
dev_free callback in snd_device chain, and this would do almost all
job.  That's why we can leave empty as default there.

> And on the long run things 
> should probably be re-factored to do all memory freeing in a subdevice 
> specific release function.

This patchset is one step toward the simplification, indeed.

But, what do you have in mind when you write "a subsystem specific
release function"?


thanks,

Takashi