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Date:   Fri, 29 Nov 2019 15:31:08 +0100
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Pavel Machek <pavel@denx.de>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Huazhong Tan <tanhuazhong@huawei.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 4.19 185/306] net: hns3: bugfix for buffer not free
 problem during resetting
Message-ID: <20191129143108.GA3708972@kroah.com>
References: <20191127203114.766709977@linuxfoundation.org>
 <20191127203128.798931840@linuxfoundation.org>
 <20191129110010.GA4313@amd>
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On Fri, Nov 29, 2019 at 12:00:10PM +0100, Pavel Machek wrote:
> Hi!
> 
> > From: Huazhong Tan <tanhuazhong@huawei.com>
> > 
> > [ Upstream commit 73b907a083b8a8c1c62cb494bc9fbe6ae086c460 ]
> > 
> > When hns3_get_ring_config()/hns3_queue_to_ring()/
> > hns3_get_vector_ring_chain() failed during resetting, the allocated
> > memory has not been freed before these three functions return. So
> > this patch adds error handler in these functions to fix it.
> 
> Correct me if I'm wrong, but... this introduces use-after-free:
> 
> > @@ -2592,6 +2592,16 @@ static int hns3_get_vector_ring_chain(struct hns3_enet_tqp_vector *tqp_vector,
> >  	}
> >  
> >  	return 0;
> > +
> > +err_free_chain:
> > +	cur_chain = head->next;
> > +	while (cur_chain) {
> > +		chain = cur_chain->next;
> > +		devm_kfree(&pdev->dev, chain);
> > +		cur_chain = chain;
> > +	}
> 
> Lets take two iterations:
> 
> > +		chain = cur_chain->next;
> > +		devm_kfree(&pdev->dev, chain);
> chain freed here.
> > +		cur_chain = chain;
> 
> > +		chain = cur_chain->next;
> chain->next accessed here, after free.
> > +		devm_kfree(&pdev->dev, chain);
> > +		cur_chain = chain;
> 
> Should it do devm_kfree(&pdev->dev, cur_chain); ?

I think Sasha tried to backport a fix for this patch, but that fix broke
the build :(

If you want to provide a working backport, I'll be glad to take it.

thanks,

greg k-h