linux-kernel - Re: [PATCH] bus: fsl-mc: fix an error handling in fsl_mc_device

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Message-ID: <aU5W1HKL4amapLrM@stanley.mountain>
Date: Fri, 26 Dec 2025 12:35:16 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>
Cc: Haoxiang Li <lihaoxiang@...c.iscas.ac.cn>, ioana.ciornei@....com,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Su Hui <suhui@...china.com>
Subject: Re: [PATCH] bus: fsl-mc: fix an error handling in fsl_mc_device_add()

On Wed, Dec 24, 2025 at 10:57:52AM +0100, Christophe Leroy (CS GROUP) wrote:
> 
> 
> Le 24/12/2025 à 08:54, Dan Carpenter a écrit :
> > On Tue, Dec 23, 2025 at 04:34:44PM +0100, Christophe Leroy (CS GROUP) wrote:
> > > 
> > > 
> > > Le 22/12/2025 à 08:49, Haoxiang Li a écrit :
> > > > If device_add() fails, call put_device() to drop the device
> > > > reference and do the cleanp.
> > > > 
> > > > Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> > > > Closes: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2Fb767348e-d89c-416e-acea-1ebbff3bea20%40stanley.mountain%2F&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7Cfd3865935a164c2083cc08de42c1b5a5%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639021596902232212%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=j5%2BqptzXvrxcnaaH3PIDorAYMexoPmf3PWi5GbpVD9s%3D&reserved=0
> > > > Signed-off-by: Su Hui <suhui@...china.com>
> > > > Signed-off-by: Haoxiang Li <lihaoxiang@...c.iscas.ac.cn>
> > > > ---
> > > >    drivers/bus/fsl-mc/fsl-mc-bus.c | 3 ++-
> > > >    1 file changed, 2 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
> > > > index 25845c04e562..90a2107a9905 100644
> > > > --- a/drivers/bus/fsl-mc/fsl-mc-bus.c
> > > > +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
> > > > @@ -896,7 +896,8 @@ int fsl_mc_device_add(struct fsl_mc_obj_desc *obj_desc,
> > > >    		dev_err(parent_dev,
> > > >    			"device_add() failed for device %s: %d\n",
> > > >    			dev_name(&mc_dev->dev), error);
> > > > -		goto error_cleanup_dev;
> > > > +		put_device(&mc_dev->dev)
> > > 
> > > This change has obviously not been tested, not even built.
> > > 
> > 
> > Yeah, it doesn't build.
> > 
> > > And by droping the goto, the kfree() are not done anymore, leaking
> > > mc_bus/mc_dev p kzalloced areas.
> > > 
> > 
> > Calling put_device() triggers fsl_mc_device_release() which does the
> > free.
> 
> Ok, then this needs to be said in the commit message.
> 
> By the way I'm a bit puzzled by the device_add() doc versus the
> put_device(), because it looks like device_add() already calls put_device()
> in its error path, see
> https://elixir.bootlin.com/linux/v6.19-rc2/source/drivers/base/core.c#L3716
> 

It's refcounted.  It calls dev = get_device(dev) at the start so it
gives up its own reference at the end.  We need another put_device() to
free everything.

regards,
dan carpetner