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

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Message-ID: <20190430145613.7tokgyqjsuxlyh2g@pathway.suse.cz>
Date:   Tue, 30 Apr 2019 16:56:13 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     "Tobin C. Harding" <tobin@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        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 2019-04-30 10:15:33, 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.

I see, the ref count is always initialized to 1 via:

  + kobject_init_and_add()
    + kobject_init()
      + kobject_init_internal()
	+ kref_init()


> 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;

We could actually get rid of the custom kobj_added. Intead, we could
check for kobj->state_initialized in the various klp_free* functions.

Best Regards,
Petr