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From: Christoph Hellwig <hch@lst.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: jasowang@redhat.com, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	iommu@lists.linux-foundation.org, eric.auger.pro@gmail.com,
	robin.murphy@arm.com, hch@lst.de
Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call
Date: Tue, 23 Jul 2019 17:38:30 +0200	[thread overview]
Message-ID: <20190723153830.GD720@lst.de> (raw)
In-Reply-To: <20190722112704-mutt-send-email-mst@kernel.org>

On Mon, Jul 22, 2019 at 11:33:35AM -0400, Michael S. Tsirkin wrote:
> On Mon, Jul 22, 2019 at 04:55:09PM +0200, Eric Auger wrote:
> > Do not call dma_max_mapping_size for devices that have no DMA
> > mask set, otherwise we can hit a NULL pointer dereference.
> > 
> > This occurs when a virtio-blk-pci device is protected with
> > a virtual IOMMU.
> > 
> > Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()")
> > Signed-off-by: Eric Auger <eric.auger@redhat.com>
> > Suggested-by: Christoph Hellwig <hch@lst.de>
> 
> Christoph, I wonder why did you suggest this?
> The connection between dma_mask and dma_max_mapping_size
> is far from obvious.  The documentation doesn't exist.
> Do we really have to teach all users about this hack?
> Why not just make dma_max_mapping_size DTRT?

Because we should not call into dma API functions for devices that
are not DMA capable.
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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Eric Auger <eric.auger@redhat.com>,
	eric.auger.pro@gmail.com, hch@lst.de, m.szyprowski@samsung.com,
	robin.murphy@arm.com, jasowang@redhat.com,
	virtualization@lists.linux-foundation.org,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call
Date: Tue, 23 Jul 2019 17:38:30 +0200	[thread overview]
Message-ID: <20190723153830.GD720@lst.de> (raw)
In-Reply-To: <20190722112704-mutt-send-email-mst@kernel.org>

On Mon, Jul 22, 2019 at 11:33:35AM -0400, Michael S. Tsirkin wrote:
> On Mon, Jul 22, 2019 at 04:55:09PM +0200, Eric Auger wrote:
> > Do not call dma_max_mapping_size for devices that have no DMA
> > mask set, otherwise we can hit a NULL pointer dereference.
> > 
> > This occurs when a virtio-blk-pci device is protected with
> > a virtual IOMMU.
> > 
> > Fixes: e6d6dd6c875e ("virtio: Introduce virtio_max_dma_size()")
> > Signed-off-by: Eric Auger <eric.auger@redhat.com>
> > Suggested-by: Christoph Hellwig <hch@lst.de>
> 
> Christoph, I wonder why did you suggest this?
> The connection between dma_mask and dma_max_mapping_size
> is far from obvious.  The documentation doesn't exist.
> Do we really have to teach all users about this hack?
> Why not just make dma_max_mapping_size DTRT?

Because we should not call into dma API functions for devices that
are not DMA capable.

  parent reply	other threads:[~2019-07-23 15:38 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-22 14:55 [PATCH 0/2] Fix NULL pointer dereference with virtio-blk-pci and virtual IOMMU Eric Auger
2019-07-22 14:55 ` Eric Auger
2019-07-22 14:55 ` [PATCH 1/2] dma-mapping: Protect dma_addressing_limited against NULL dma_mask Eric Auger
2019-07-22 14:55 ` Eric Auger
2019-07-22 14:55   ` Eric Auger
2019-07-22 15:26   ` Christoph Hellwig
2019-07-22 15:26     ` Christoph Hellwig
2019-07-22 15:46     ` Auger Eric
2019-07-22 15:46     ` Auger Eric
2019-07-22 15:46       ` Auger Eric
2019-07-22 15:26   ` Christoph Hellwig
2019-07-22 14:55 ` [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call Eric Auger
2019-07-22 14:55   ` Eric Auger
2019-07-22 15:27   ` Christoph Hellwig
2019-07-22 15:27     ` Christoph Hellwig
2019-07-22 15:39     ` Michael S. Tsirkin
2019-07-22 15:39     ` Michael S. Tsirkin
2019-07-22 15:39       ` Michael S. Tsirkin
2019-07-22 15:27   ` Christoph Hellwig
2019-07-22 15:33   ` Michael S. Tsirkin
2019-07-22 15:33   ` Michael S. Tsirkin
2019-07-22 15:33     ` Michael S. Tsirkin
2019-07-23 15:38     ` Christoph Hellwig
2019-07-23 15:38     ` Christoph Hellwig [this message]
2019-07-23 15:38       ` Christoph Hellwig
2019-07-23 15:47       ` Michael S. Tsirkin
2019-07-23 15:47         ` Michael S. Tsirkin
2019-07-23 15:47       ` Michael S. Tsirkin
2019-07-22 15:36   ` Robin Murphy
2019-07-22 15:36   ` Robin Murphy
2019-07-22 15:36     ` Robin Murphy
2019-07-22 15:45     ` Michael S. Tsirkin
2019-07-22 15:45       ` Michael S. Tsirkin
2019-07-22 15:45     ` Michael S. Tsirkin
2019-07-23 15:38     ` Christoph Hellwig
2019-07-23 15:38       ` Christoph Hellwig
2019-07-23 15:38       ` Christoph Hellwig
2019-07-24 22:10       ` Michael S. Tsirkin
2019-07-24 22:10         ` Michael S. Tsirkin
2019-07-25  5:25         ` Christoph Hellwig
2019-07-25  5:25           ` Christoph Hellwig
2019-07-25  5:25         ` Christoph Hellwig
2019-07-24 22:10       ` Michael S. Tsirkin
2019-07-25 11:53       ` Auger Eric
2019-07-25 11:53       ` Auger Eric
2019-07-25 11:53         ` Auger Eric
2019-07-25 13:04         ` Christoph Hellwig
2019-07-25 13:04         ` Christoph Hellwig
2019-07-25 13:04           ` Christoph Hellwig
2019-07-25 16:32           ` Auger Eric
2019-07-25 16:32           ` Auger Eric
2019-07-25 16:32             ` Auger Eric
2019-07-22 14:55 ` Eric Auger

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