linux-kernel - Re: [PATCH 3/7] net: stmmac: Check for DMA mapping errors

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Date:   Thu, 9 Mar 2017 20:29:09 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Mikko Perttunen <cyndis@...si.fi>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Alexandre Courbot <gnurou@...il.com>,
        Jon Hunter <jonathanh@...dia.com>, netdev@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] net: stmmac: Check for DMA mapping errors

On Mon, Feb 27, 2017 at 11:37:24AM +0200, Mikko Perttunen wrote:
> On 23.02.2017 19:24, Thierry Reding wrote:
> > From: Thierry Reding <treding@...dia.com>
> > 
> > When DMA mapping an SKB fragment, the mapping must be checked for
> > errors, otherwise the DMA debug code will complain upon unmap.
> > 
> > Signed-off-by: Thierry Reding <treding@...dia.com>
> > ---
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 6b7a5ce19589..d7387919bdb6 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -2072,6 +2072,8 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
> >  		des = skb_frag_dma_map(priv->device, frag, 0,
> >  				       skb_frag_size(frag),
> >  				       DMA_TO_DEVICE);
> > +		if (dma_mapping_error(priv->device, des))
> > +			goto dma_map_err;
> 
> If this map fails, we should also unmap the previously mapped fragments and
> the separate mapping made using dma_map_single.

That's already taken care of via the dma_map_err label:

	dev_kfree_skb()
	  consume_skb()
	    __kfree_skb()
	      skb_release_all()
	        skb_release_data()

Thierry

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