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From: Christoph Hellwig <hch@lst.de>
To: Thomas Tai <thomas.tai@oracle.com>
Cc: konrad.wilk@oracle.com, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, robin.murphy@arm.com,
	hch@lst.de
Subject: Re: [PATCH] dma-direct: Fix potential NULL pointer dereference
Date: Tue, 15 Sep 2020 16:08:30 +0200	[thread overview]
Message-ID: <20200915140830.GA14958@lst.de> (raw)
In-Reply-To: <20200915140719.GA14831@lst.de>

On Tue, Sep 15, 2020 at 04:07:19PM +0200, Christoph Hellwig wrote:
> On Tue, Sep 15, 2020 at 08:03:14AM -0600, Thomas Tai wrote:
> > When booting the kernel v5.9-rc4 on a VM, the kernel would panic when
> > printing a warning message in swiotlb_map(). It is because dev->dma_mask
> > can potentially be a null pointer. Using the dma_get_mask() macro can
> > avoid the NULL pointer dereference.
> 
> dma_mask must not be zero.  This means drm is calling DMA API functions
> on something weird.  This needs to be fixed in the caller.

s/zero/NULL/, but the point stands.
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Thomas Tai <thomas.tai@oracle.com>
Cc: konrad.wilk@oracle.com, m.szyprowski@samsung.com, hch@lst.de,
	robin.murphy@arm.com, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dma-direct: Fix potential NULL pointer dereference
Date: Tue, 15 Sep 2020 16:08:30 +0200	[thread overview]
Message-ID: <20200915140830.GA14958@lst.de> (raw)
In-Reply-To: <20200915140719.GA14831@lst.de>

On Tue, Sep 15, 2020 at 04:07:19PM +0200, Christoph Hellwig wrote:
> On Tue, Sep 15, 2020 at 08:03:14AM -0600, Thomas Tai wrote:
> > When booting the kernel v5.9-rc4 on a VM, the kernel would panic when
> > printing a warning message in swiotlb_map(). It is because dev->dma_mask
> > can potentially be a null pointer. Using the dma_get_mask() macro can
> > avoid the NULL pointer dereference.
> 
> dma_mask must not be zero.  This means drm is calling DMA API functions
> on something weird.  This needs to be fixed in the caller.

s/zero/NULL/, but the point stands.

  reply	other threads:[~2020-09-15 14:08 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15 14:03 [PATCH] dma-direct: Fix potential NULL pointer dereference Thomas Tai
2020-09-15 14:03 ` Thomas Tai
2020-09-15 14:07 ` Christoph Hellwig
2020-09-15 14:07   ` Christoph Hellwig
2020-09-15 14:08   ` Christoph Hellwig [this message]
2020-09-15 14:08     ` Christoph Hellwig
2020-09-15 14:11   ` Thomas Tai
2020-09-15 14:11     ` Thomas Tai
2020-09-15 14:26     ` Christoph Hellwig
2020-09-15 14:26       ` Christoph Hellwig
2020-09-15 14:40       ` Thomas Tai
2020-09-15 14:40         ` Thomas Tai
2020-09-15 15:09         ` Christoph Hellwig
2020-09-15 15:09           ` Christoph Hellwig
2020-09-15 15:12           ` Thomas Tai
2020-09-15 15:12             ` Thomas Tai
2020-09-15 20:46           ` Thomas Tai
2020-09-15 20:46             ` Thomas Tai
2020-09-16  6:19             ` Christoph Hellwig
2020-09-16  6:19               ` Christoph Hellwig

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