linux-kernel - Re: [PATCH 4.4 35/46] ravb: unmap descriptors when freeing rings

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Date:   Mon, 3 Jul 2017 14:52:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>
Cc:     Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>,
        Simon Horman <horms+renesas@...ge.net.au>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: Re: [PATCH 4.4 35/46] ravb: unmap descriptors when freeing rings

On Thu, Jun 29, 2017 at 02:58:09PM +0100, Ben Hutchings wrote:
> On Thu, 2017-06-15 at 19:52 +0200, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> > 
> > 
> > [ Upstream commit a47b70ea86bdeb3091341f5ae3ef580f1a1ad822 ]
> > 
> > "swiotlb buffer is full" errors occur after repeated initialisation of a
> > device - f.e. suspend/resume or ip link set up/down. This is because memory
> > mapped using dma_map_single() in ravb_ring_format() and ravb_start_xmit()
> > is not released.  Resolve this problem by unmapping descriptors when
> > freeing rings.
> 
> This should be followed by:
> 
> commit 79514ef670e9e575a1fe36922268c439d0f0ca8a
> Author: Eugeniu Rosca <erosca@...adit-jv.com>
> Date:   Tue Jun 6 00:08:10 2017 +0200
> 
>     ravb: Fix use-after-free on `ifconfig eth0 down`

Thanks, now queued up.

> But also, this loop looks wrong:
> 
> [...]
> >  	if (priv->rx_ring[q]) {
> > +		for (i = 0; i < priv->num_rx_ring[q]; i++) {
> > +			struct ravb_ex_rx_desc *desc = &priv->rx_ring[q][i];
> > +
> > +			if (!dma_mapping_error(ndev->dev.parent,
> > +					       le32_to_cpu(desc->dptr)))
> > +				dma_unmap_single(ndev->dev.parent,
> > +						 le32_to_cpu(desc->dptr),
> > +						 PKT_BUF_SZ,
> > +						 DMA_FROM_DEVICE);
> > +		}
> [...]
> 
> It's possible that the driver hasn't filled (or attempted to fill or
> refill) every RX descriptor, so this could result in a double-unmap.  I
> think this needs to use cur_rx and dirty_rx to determine which
> descriptors to process.

I'll let Kazuya fix that :)

thanks,

greg k-h