linux-kernel - Re: [PATCH] fw_cfg: Fix memory leak in fw_cfg_register

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Message-ID: <YaZc4LbX5hrJDnec@hovoldconsulting.com>
Date:   Tue, 30 Nov 2021 18:18:24 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Philippe Mathieu-Daudé <philmd@...hat.com>
Cc:     Miaoqian Lin <linmq006@...il.com>, Qiushi Wu <wu000273@....edu>,
        qemu-devel@...gnu.org, linux-kernel@...r.kernel.org,
        Gabriel Somlo <somlo@....edu>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH] fw_cfg: Fix memory leak in fw_cfg_register_file

On Tue, Nov 16, 2021 at 04:28:34PM +0100, Philippe Mathieu-Daudé wrote:
> On 11/16/21 12:42, Miaoqian Lin wrote:
> > When kobject_init_and_add() fails, entry should be freed just like
> > when sysfs_create_bin_file() fails.
> > 
> 
> Fixes: fe3c60684377 ("firmware: Fix a reference count leak.")
> Reviewed-by: Philippe Mathieu-Daudé <philmd@...hat.com>

No, no. This patch is completely bogus and would introduce a double
free.

> > Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> > ---
> >  drivers/firmware/qemu_fw_cfg.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
> > index 172c751a4f6c..0f404777f016 100644
> > --- a/drivers/firmware/qemu_fw_cfg.c
> > +++ b/drivers/firmware/qemu_fw_cfg.c
> > @@ -608,6 +608,7 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
> >  				   fw_cfg_sel_ko, "%d", entry->select);
> >  	if (err) {
> >  		kobject_put(&entry->kobj);
> > +		kfree(entry);

entry would already have been freed by kobject_put() and
fw_cfg_sysfs_release_entry() here.

> >  		return err;
> >  	}
> >  
> > 

Doesn't look like this patch has been picked up yet, so:

	NAK.

Johan