linux-kernel - Re: [PATCH] arm64/dma-mapping: Fix null-pointer check

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Date:   Mon, 12 Jun 2017 13:50:28 -0700
From:   Olav Haugan <ohaugan@...eaurora.org>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     will.deacon@....com, robin.murphy@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm64/dma-mapping: Fix null-pointer check

On 17-06-12 13:29:04, Catalin Marinas wrote:
> On Sat, Jun 10, 2017 at 12:41:10PM -0700, Olav Haugan wrote:
> > @@ -149,6 +140,11 @@ static void *__dma_alloc(struct device *dev, size_t size,
> >  	bool coherent = is_device_dma_coherent(dev);
> >  	pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL, false);
> >  
> > +	if (!dev) {
> > +		WARN_ONCE(1, "Use an actual device structure for DMA allocation\n");
> > +		return NULL;
> > +	}
> > +
> >  	size = PAGE_ALIGN(size);
> >  
> >  	if (!coherent && !gfpflags_allow_blocking(flags)) {
> > @@ -192,8 +188,13 @@ static void __dma_free(struct device *dev, size_t size,
> >  		       void *vaddr, dma_addr_t dma_handle,
> >  		       unsigned long attrs)
> >  {
> > -	void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
> > +	void *swiotlb_addr;
> >  
> > +	if (!dev) {
> > +		WARN_ONCE(1, "Use an actual device structure for DMA free\n");
> > +		return;
> > +	}
> > +	swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
> 
> I don't think we need the checks anymore. With commit 1dccb598df54
> ("arm64: simplify dma_get_ops") __generic_dma_ops() returns
> dummy_dma_ops when dev == NULL, so the above __dma_alloc/__dma_free
> functions would not be called.
> 

We don't need the check in is_device_dma_coherent() either then right?

-- 
.Olav

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