From: Christoph Hellwig <hch@lst.de>
To: Walter Wu <walter-zh.wu@mediatek.com>
Cc: wsd_upstream <wsd_upstream@mediatek.com>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING
Date: Tue, 2 Nov 2021 07:41:55 +0100 [thread overview]
Message-ID: <20211102064155.GA27749@lst.de> (raw)
In-Reply-To: <20211101031558.7184-1-walter-zh.wu@mediatek.com>
As others pointed out, DMA_ATTR_NO_KERNEL_MAPPING just means the
caller can't rely on a kernel mapping. So the "fix" here is
wrong. That being said for cases where we can easily remove a page
from the kernel mapping it would be nice to do to:
a) improve security
b) as a debug check to see that no one actually tries to access it
> + /* remove kernel mapping for pages */
> + set_memory_valid((unsigned long)phys_to_virt(dma_to_phys(dev, *dma_handle)),
Please avoid overly long lines. Also this function only exists for arm64
also and others pointed out won't work for all cases.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
wsd_upstream <wsd_upstream@mediatek.com>,
linux-mediatek@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING
Date: Tue, 2 Nov 2021 07:41:55 +0100 [thread overview]
Message-ID: <20211102064155.GA27749@lst.de> (raw)
In-Reply-To: <20211101031558.7184-1-walter-zh.wu@mediatek.com>
As others pointed out, DMA_ATTR_NO_KERNEL_MAPPING just means the
caller can't rely on a kernel mapping. So the "fix" here is
wrong. That being said for cases where we can easily remove a page
from the kernel mapping it would be nice to do to:
a) improve security
b) as a debug check to see that no one actually tries to access it
> + /* remove kernel mapping for pages */
> + set_memory_valid((unsigned long)phys_to_virt(dma_to_phys(dev, *dma_handle)),
Please avoid overly long lines. Also this function only exists for arm64
also and others pointed out won't work for all cases.
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
wsd_upstream <wsd_upstream@mediatek.com>,
linux-mediatek@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING
Date: Tue, 2 Nov 2021 07:41:55 +0100 [thread overview]
Message-ID: <20211102064155.GA27749@lst.de> (raw)
In-Reply-To: <20211101031558.7184-1-walter-zh.wu@mediatek.com>
As others pointed out, DMA_ATTR_NO_KERNEL_MAPPING just means the
caller can't rely on a kernel mapping. So the "fix" here is
wrong. That being said for cases where we can easily remove a page
from the kernel mapping it would be nice to do to:
a) improve security
b) as a debug check to see that no one actually tries to access it
> + /* remove kernel mapping for pages */
> + set_memory_valid((unsigned long)phys_to_virt(dma_to_phys(dev, *dma_handle)),
Please avoid overly long lines. Also this function only exists for arm64
also and others pointed out won't work for all cases.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
wsd_upstream <wsd_upstream@mediatek.com>,
linux-mediatek@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING
Date: Tue, 2 Nov 2021 07:41:55 +0100 [thread overview]
Message-ID: <20211102064155.GA27749@lst.de> (raw)
In-Reply-To: <20211101031558.7184-1-walter-zh.wu@mediatek.com>
As others pointed out, DMA_ATTR_NO_KERNEL_MAPPING just means the
caller can't rely on a kernel mapping. So the "fix" here is
wrong. That being said for cases where we can easily remove a page
from the kernel mapping it would be nice to do to:
a) improve security
b) as a debug check to see that no one actually tries to access it
> + /* remove kernel mapping for pages */
> + set_memory_valid((unsigned long)phys_to_virt(dma_to_phys(dev, *dma_handle)),
Please avoid overly long lines. Also this function only exists for arm64
also and others pointed out won't work for all cases.
next prev parent reply other threads:[~2021-11-02 6:42 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 3:15 [PATCH] dma-direct: fix DMA_ATTR_NO_KERNEL_MAPPING Walter Wu
2021-11-01 3:15 ` Walter Wu
2021-11-01 3:15 ` Walter Wu
2021-11-01 3:15 ` Walter Wu
2021-11-01 6:10 ` kernel test robot
2021-11-01 6:10 ` kernel test robot
2021-11-01 6:10 ` kernel test robot
2021-11-01 6:10 ` kernel test robot
2021-11-01 6:10 ` kernel test robot
2021-11-01 8:34 ` Ard Biesheuvel
2021-11-01 8:34 ` Ard Biesheuvel
2021-11-01 8:34 ` Ard Biesheuvel
2021-11-01 8:34 ` Ard Biesheuvel
2021-11-01 12:20 ` Walter Wu
2021-11-01 12:20 ` Walter Wu
2021-11-01 12:20 ` Walter Wu
2021-11-01 12:20 ` Walter Wu
2021-11-01 14:17 ` Ard Biesheuvel
2021-11-01 14:17 ` Ard Biesheuvel
2021-11-01 14:17 ` Ard Biesheuvel
2021-11-01 14:17 ` Ard Biesheuvel
2021-11-02 3:21 ` Walter Wu
2021-11-02 3:21 ` Walter Wu
2021-11-02 3:21 ` Walter Wu
2021-11-02 3:21 ` Walter Wu
2021-11-02 6:43 ` Christoph Hellwig
2021-11-02 6:43 ` Christoph Hellwig
2021-11-02 6:43 ` Christoph Hellwig
2021-11-02 6:43 ` Christoph Hellwig
2021-11-01 10:29 ` Robin Murphy
2021-11-01 10:29 ` Robin Murphy
2021-11-01 10:29 ` Robin Murphy
2021-11-01 10:29 ` Robin Murphy
2021-11-01 12:07 ` Walter Wu
2021-11-01 12:07 ` Walter Wu
2021-11-01 12:07 ` Walter Wu
2021-11-01 12:07 ` Walter Wu
2021-11-02 6:41 ` Christoph Hellwig [this message]
2021-11-02 6:41 ` Christoph Hellwig
2021-11-02 6:41 ` Christoph Hellwig
2021-11-02 6:41 ` Christoph Hellwig
2021-11-02 7:08 ` Walter Wu
2021-11-02 7:08 ` Walter Wu
2021-11-02 7:08 ` Walter Wu
2021-11-02 7:08 ` Walter Wu
2021-11-02 7:26 ` Walter Wu
2021-11-02 7:26 ` Walter Wu
2021-11-02 7:26 ` Walter Wu
2021-11-02 7:26 ` Walter Wu
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