linux-kernel - Re: [PATCH] dma-mapping: Protect dma_addressing_limited against NULL dma

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Date:   Mon, 22 Jul 2019 13:43:03 +0200
From:   Christoph Hellwig <hch@....de>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, hch@....de, m.szyprowski@...sung.com,
        robin.murphy@....com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma-mapping: Protect dma_addressing_limited against
 NULL dma_mask

I posted a fix that takes care of this in SCSI this morning:

https://marc.info/?l=linux-scsi&m=156378725427719&w=2

I suspect for virtio-blk we should do the same.

>  static inline bool dma_addressing_limited(struct device *dev)
>  {
> -	return min_not_zero(*dev->dma_mask, dev->bus_dma_mask) <
> -		dma_get_required_mask(dev);
> +	return dev->dma_mask ? min_not_zero(*dev->dma_mask, dev->bus_dma_mask) <
> +		dma_get_required_mask(dev) : false;

But to be on the safe side we could still do an early return here,
but it should have a WARN_ON_ONCE.