linux-kernel - Re: [PATCH 4.19 84/90] cfg80211: fix memory leak of wiphy device name

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Date:   Tue, 25 Jun 2019 15:33:35 -0700
From:   Eric Biggers <ebiggers@...gle.com>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        syzbot+7fddca22578bc67c3fe4@...kaller.appspotmail.com,
        Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH 4.19 84/90] cfg80211: fix memory leak of wiphy device name

On Tue, Jun 25, 2019 at 11:51:36PM +0200, Pavel Machek wrote:
> Hi!
> 
> > From: Eric Biggers <ebiggers@...gle.com>
> > 
> > commit 4f488fbca2a86cc7714a128952eead92cac279ab upstream.
> > 
> > In wiphy_new_nm(), if an error occurs after dev_set_name() and
> > device_initialize() have already been called, it's necessary to call
> > put_device() (via wiphy_free()) to avoid a memory leak.
> ....
> > --- a/net/wireless/core.c
> > +++ b/net/wireless/core.c
> > @@ -498,7 +498,7 @@ use_default_name:
> >  				   &rdev->rfkill_ops, rdev);
> >  
> >  	if (!rdev->rfkill) {
> > -		kfree(rdev);
> > +		wiphy_free(&rdev->wiphy);
> >  		return NULL;
> >  	}
> 
> Is kfree(rdev) still neccessary?
> drivers/net/wireless/marvell/libertas/cfg.c seems to suggest so.
> 

No, because it's freed by:

    wiphy_free()
        => put_device()
            => wiphy_dev_release()
                => cfg80211_dev_free()
		    => kfree(rdev)

drivers/net/wireless/marvell/libertas/cfg.c is different because there the
struct wiphy is separately allocated from the struct wireless_dev that's being
freed afterwards.

- Eric