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Date: Tue, 15 Sep 2020 11:12:28 -0400 From: Thomas Tai <thomas.tai@...cle.com> To: Christoph Hellwig <hch@....de> Cc: konrad.wilk@...cle.com, m.szyprowski@...sung.com, robin.murphy@....com, iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] dma-direct: Fix potential NULL pointer dereference On 2020-09-15 11:09 a.m., Christoph Hellwig wrote: > On Tue, Sep 15, 2020 at 10:40:39AM -0400, Thomas Tai wrote: >>> +++ b/include/linux/dma-direct.h >>> @@ -62,9 +62,6 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, >>> { >>> dma_addr_t end = addr + size - 1; >>> - if (!dev->dma_mask) >>> - return false; >>> - >> >> I am concerned that some drivers may rely on this NULL checking. Would you >> think we can keep this checking and use the following WARN_ON_ONCE()? > > dma_capable is not a helper for drivers, but just for dma-direct > and related code. And this patch adds the checks for the three > places how we call into the ->map* methods. > Ok. That sounds good to me. I will make the suggested changes and run some tests before sending out the V2 patch. Thank you, Thomas
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