linux-kernel - Re: [PATCH 1/2] livepatch: Fix kobject memleak

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Message-ID: <20190430104638.GA8137@kroah.com>
Date:   Tue, 30 Apr 2019 12:46:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     "Tobin C. Harding" <tobin@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>, Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] livepatch: Fix kobject memleak

On Tue, Apr 30, 2019 at 12:44:55PM +0200, Miroslav Benes wrote:
> On Tue, 30 Apr 2019, Greg Kroah-Hartman wrote:
> 
> > On Tue, Apr 30, 2019 at 10:15:33AM +1000, Tobin C. Harding wrote:
> > > Currently error return from kobject_init_and_add() is not followed by a
> > > call to kobject_put().  This means there is a memory leak.
> > > 
> > > Add call to kobject_put() in error path of kobject_init_and_add().
> > > 
> > > Signed-off-by: Tobin C. Harding <tobin@...nel.org>
> > 
> > Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> Well, it does not even compile...

The idea is correct :)

> On Tue, 30 Apr 2019, Tobin C. Harding wrote:
> 
> > Currently error return from kobject_init_and_add() is not followed by a
> > call to kobject_put().  This means there is a memory leak.
> > 
> > Add call to kobject_put() in error path of kobject_init_and_add().
> > 
> > Signed-off-by: Tobin C. Harding <tobin@...nel.org>
> > ---
> >  kernel/livepatch/core.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> > 
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index eb0ee10a1981..98a7bec41faa 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -727,7 +727,9 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
> >  	ret = kobject_init_and_add(&func->kobj, &klp_ktype_func,
> >  				   &obj->kobj, "%s,%lu", func->old_name,
> >  				   func->old_sympos ? func->old_sympos : 1);
> > -	if (!ret)
> > +	if (ret)
> > +		kobject_put(&func->kobj);
> > +	else
> >  		func->kobj_added = true;
> >  
> >  	return ret;
> > @@ -803,8 +805,10 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
> >  	name = klp_is_module(obj) ? obj->name : "vmlinux";
> >  	ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
> >  				   &patch->kobj, "%s", name);
> > -	if (ret)
> > +	if (ret) {
> > +		kobject_put(&func->kobj);
> 
> kobject_put(&obj->kobj); I suppose.

Yeah, that makes it better, sorry for not catching that in the review :(

greg k-h