linux-kernel - Re: [PATCH 4.19 25/48] firmware: Fix a reference count leak.

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Date:   Mon, 10 Aug 2020 18:41:51 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Qiushi Wu <wu000273@....edu>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 25/48] firmware: Fix a reference count leak.

Hi!

> From: Qiushi Wu <wu000273@....edu>
> 
> [ Upstream commit fe3c60684377d5ad9b0569b87ed3e26e12c8173b ]
> 
> kobject_init_and_add() takes reference even when it fails.
> If this function returns an error, kobject_put() must be called to
> properly clean up the memory associated with the object.
> Callback function fw_cfg_sysfs_release_entry() in kobject_put()
> can handle the pointer "entry" properly.

Okay, but... does that mean err_add_raw: should be using
kobject_put(), too (w/o the kfree)? It is strange to have different
error handling for different error paths.

Best regards,
								Pavel

> +++ b/drivers/firmware/qemu_fw_cfg.c
> @@ -605,8 +605,10 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
>  	/* register entry under "/sys/firmware/qemu_fw_cfg/by_key/" */
>  	err = kobject_init_and_add(&entry->kobj, &fw_cfg_sysfs_entry_ktype,
>  				   fw_cfg_sel_ko, "%d", entry->select);
> -	if (err)
> -		goto err_register;
> +	if (err) {
> +		kobject_put(&entry->kobj);
> +		return err;
> +	}
>  
>  	/* add raw binary content access */
>  	err = sysfs_create_bin_file(&entry->kobj, &fw_cfg_sysfs_attr_raw);
> @@ -622,7 +624,6 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
>  
>  err_add_raw:
>  	kobject_del(&entry->kobj);
> -err_register:
>  	kfree(entry);
>  	return err;
>  }

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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