Re: [PATCH] net: mdiobus: Fix memory leak in __mdiobus_register

[Dongliang Mu]

On Tue, Sep 28, 2021 at 11:41 PM Russell King (Oracle)
<linux@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Sep 28, 2021 at 04:52:07PM +0300, Dan Carpenter wrote:
> > On Tue, Sep 28, 2021 at 01:58:00PM +0100, Russell King (Oracle) wrote:
> > >
> > > This thread seems to be getting out of hand.
> >
> > The thread was closed.  We need to revert Yanfei's patch and apply
> > Pavel's patch.  He's going to resend.
> >
> > > So, I would suggest a simple fix is to set bus->state to
> > > MDIOBUS_UNREGISTERED immediately _after_ the successful
> > > device_register().
> >
> > Not after.  It has to be set to MDIOBUS_UNREGISTERED if device_register()
> > fails, otherwise there will still be a leak.
>
> Ah yes, you are correct - the device name may not be freed. Also...
>
>  * NOTE: _Never_ directly free @dev after calling this function, even
>  * if it returned an error! Always use put_device() to give up your
>  * reference instead.
>
> So yes, we must set to MDIOBUS_UNREGISTERED even if device_register()
> fails.
>

So we have reached an agreement. Pavel's patch fixes the syzbot link
[1], other than Yanfei's patch. However, Yanfei's patch also fixes
another memory link nearby.

Right?

[1] https://syzkaller.appspot.com/bug?id=fa99459691911a0369622248e0f4e3285fcedd97

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