From: Walter Wu <walter-zh.wu@mediatek.com>
To: Christoph Hellwig <hch@lst.de>
Cc: 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 15:08:11 +0800 [thread overview]
Message-ID: <8903df2ad1ae1e0dfaafb3766beef7d0ec156f28.camel@mediatek.com> (raw)
In-Reply-To: <20211102064155.GA27749@lst.de>
Hi Cristoph,
On Tue, 2021-11-02 at 07:41 +0100, Christoph Hellwig wrote:
> 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
>
I will modify my commit message. Thanks for your comment.
> > + /* 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.
Got it. I will send v2 patch.
Thanks for your review and suggestion.
Walter
next prev parent reply other threads:[~2021-11-02 7:08 UTC|newest]
Thread overview: 12+ 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 6:10 ` kernel test robot
2021-11-01 8:34 ` Ard Biesheuvel
2021-11-01 12:20 ` Walter Wu
2021-11-01 14:17 ` Ard Biesheuvel
2021-11-02 3:21 ` Walter Wu
2021-11-02 6:43 ` Christoph Hellwig
2021-11-01 10:29 ` Robin Murphy
2021-11-01 12:07 ` Walter Wu
2021-11-02 6:41 ` Christoph Hellwig
2021-11-02 7:08 ` Walter Wu [this message]
2021-11-02 7:26 ` Walter Wu
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