linux-kernel - Re: [PATCH -next] staging: greybus: fix a missing-check bug in gb_lights_light

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Message-ID: <20200402160400.cvgvd3da75x2f4qe@arch-thunder.localdomain>
Date:   Thu, 2 Apr 2020 17:04:00 +0100
From:   Rui Miguel Silva <rmfrfs@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     devel@...verdev.osuosl.org, elder@...nel.org,
        Chen Zhou <chenzhou10@...wei.com>, gregkh@...uxfoundation.org,
        johan@...nel.org, linux-kernel@...r.kernel.org,
        greybus-dev@...ts.linaro.org
Subject: Re: [PATCH -next] staging: greybus: fix a missing-check bug in
 gb_lights_light_config()

Hi,
On Thu, Apr 02, 2020 at 05:22:37PM +0300, Dan Carpenter wrote:
> On Thu, Apr 02, 2020 at 02:16:18PM +0100, Rui Miguel Silva wrote:
> > > > --- a/drivers/staging/greybus/light.c
> > > > +++ b/drivers/staging/greybus/light.c
> > > > @@ -1026,7 +1026,8 @@ static int gb_lights_light_config(struct gb_lights *glights, u8 id)
> > > >  
> > > >  	light->channels_count = conf.channel_count;
> > > >  	light->name = kstrndup(conf.name, NAMES_MAX, GFP_KERNEL);
> > > > -
> > > > +	if (!light->name)
> > > > +		return -ENOMEM;
> > > >  	light->channels = kcalloc(light->channels_count,
> > > >  				  sizeof(struct gb_channel), GFP_KERNEL);
> > > >  	if (!light->channels)
> > > 
> > > The clean up in this function is non-existant.  :(
> > 
> > Yeah, this have a central point to do the cleanups, gb_lights_release,
> > since we may have other lights already configured at this point, we
> > could cleanup this specific one here, but than would need to make sure
> > all other already configure got clean also.
> 
> Central clean up functions never work correctly.

I agree.

> 
> For example, we allocate "cdev->name" in gb_lights_channel_config()
> before we register the channel later in gb_lights_register_all(glights);.
> Now imagine that the register fails.  Then when we're freeing it in
> __gb_lights_led_unregister() we see that the ->is_registered is false
> so we don't kfree(cdev->name).
> 
> That's just a small memory leak.  But there are going to be tons of
> little bugs like that.

Yeah, when I have some cycles I'll go over that error codes paths and
mitigate this kind of issues.

> 
> Anyway it doesn't affect this patch so it's fine.

Yeah, thanks.

------
Cheers,
     Rui