On Thu, Aug 10, 2017 at 11:52:42AM +0100, Phil Elwell wrote:
> On 10/08/2017 11:21, Dan Carpenter wrote:
> > The original patch did not go through the normal review process...
> >
> > On Tue, Aug 08, 2017 at 01:05:02PM +0100, Phil Elwell wrote:
> >> I'm all for fixing memory leaks, but freeing a block while it is still
> >> being used is a recipe for hard-to-debug kernel exceptions.
> >>
> >
> > This bug completely breaks the driver doesn't it? It's not very subtle
> > so it should be easy to diagnose with git bisect.
>
> It's more subtle than that - the failure isn't consistent, sometimes crashing
> and sometimes not depending on how and when memory is reused.
>
> >> 1) There is already a vchi method for freeing the instance, so use it.
> >> 2) Only call it on error, and then only before initted is false.
> >>
> >> Signed-off-by: Phil Elwell <phil@xxxxxxxxxxxxxxx>
> >> Fixes: 0adbfd4694c2 ("staging: bcm2835-audio: fix memory leak in bcm2835_audio_open_connection()")
> >> ---
> >> drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c
> >> index 5f3d8f2..89f96f3 100644
> >> --- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c
> >> +++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-vchiq.c
> >> @@ -409,6 +409,7 @@ static int bcm2835_audio_open_connection(struct bcm2835_alsa_stream *alsa_stream
> >> LOG_ERR("%s: failed to connect VCHI instance (ret=%d)\n",
> >> __func__, ret);
> >>
> >> + vchi_disconnect(vchi_instance);
> >
> > This is ugly because why are we calling disconnect() if connect() fails?
> > These functions should be symetric so disconnect only disconnects and
> > we call a different function to undo vchi_initialise().
>
> Agreed - I'm not going to change the API, but I can add a comment.
>
Nah... Please don't do that. Just create a function:
static void vchiq_free(VCHIQ_INSTANCE_T *vchi_instance)
{
kfree(vchi_instance);
}
Really vchi_initialise() is badly named and it's just a wrapper around
vchiq_initialise(). It should be deleted and vchiq_initialise() should
be renamed to allocate instead of initialize... But that's for a
separate patch.
And also we should move the kfree() out of disconnect() like I said
and instead call vchiq_free(). But again, that's for a separate patch.
Change the goto to "return -EIO." Leave the last error path as-is.
Eventually we will want to break this into two functions, one that
allocates the first vchi_instance and one that calls vc_vchi_audio_init().
But again, there are many patches needed to fix this code.
regards,
dan carpenter
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