linux-kernel - Re: [PATCH] scsi: zfcp: Fix a potential double free in zfcp_port

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Message-ID: <20230921104746.GG10864@p1gen4-pw042f0m.fritz.box>
Date:   Thu, 21 Sep 2023 12:47:46 +0200
From:   Benjamin Block <bblock@...ux.ibm.com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
Cc:     Steffen Maier <maier@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        James Bottomley <James.Bottomley@...e.de>,
        Swen Schillig <swen@...t.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mailing List linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH] scsi: zfcp: Fix a potential double free in
 zfcp_port_enqueue

On Thu, Sep 21, 2023 at 12:21:02PM +0200, Benjamin Block wrote:
> Hello Liu Dinghao,
> 
> good find.

Oh, also, please put linux-scsi on the CC list. Patches to zfcp go via
linux-scsi, not linux-s390.

> 
> On Thu, Sep 21, 2023 at 02:39:15PM +0800, Dinghao Liu wrote:
> > When device_register() fails, zfcp_port_release() will be called
> > after put_device(). As a result, the zfcp_ccw_adapter_put() after
> > err_out is redundant because it will be called in the call-back
> > function zfcp_port_release(). Remove it from this error path.
> 
> So the reference on the adapter object is doubly put, which may
> lead to a premature free of the adapter object itself. Please mention that
> either in the subject, or description; it makes it easier to see what exactly
> breaks at a glance.
> 
> > 
> > Fixes: f3450c7b9172 ("[SCSI] zfcp: Replace local reference counting with common kref")
> > Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> > ---
> >  drivers/s390/scsi/zfcp_aux.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/s390/scsi/zfcp_aux.c b/drivers/s390/scsi/zfcp_aux.c
> > index df782646e856..489e6239dedf 100644
> > --- a/drivers/s390/scsi/zfcp_aux.c
> > +++ b/drivers/s390/scsi/zfcp_aux.c
> > @@ -552,7 +552,7 @@ struct zfcp_port *zfcp_port_enqueue(struct zfcp_adapter *adapter, u64 wwpn,
> >  
> >  	if (device_register(&port->dev)) {
> >  		put_device(&port->dev);
> > -		goto err_out;
> > +		return ERR_PTR(retval);
> 
> I'd rather have a new label at the bottom, in front of the return that is
> already there, and jump to that, instead of a different function exit point.
> 
> >  	}
> >  
> >  	write_lock_irq(&adapter->port_list_lock);
> > -- 
> > 2.17.1
> > 

-- 
Best Regards, Benjamin Block        /        Linux on IBM Z Kernel Development
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