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From: David Rientjes <rientjes@google.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: hch@lst.de, m.szyprowski@samsung.com,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	thomas.lendacky@amd.com, stable@vger.kernel.org
Subject: Re: [PATCH] dma-direct: Don't over-decrypt memory
Date: Sun, 22 May 2022 18:04:51 -0700 (PDT)	[thread overview]
Message-ID: <22439fa1-5f9b-1e54-3f39-649b116574e@google.com> (raw)
In-Reply-To: <796ddc256b8a3054cb0b2f43363613463fcf0d61.1653066613.git.robin.murphy@arm.com>

On Fri, 20 May 2022, Robin Murphy wrote:

> The original x86 sev_alloc() only called set_memory_decrypted() on
> memory returned by alloc_pages_node(), so the page order calculation
> fell out of that logic. However, the common dma-direct code has several
> potential allocators, not all of which are guaranteed to round up the
> underlying allocation to a power-of-two size, so carrying over that
> calculation for the encryption/decryption size was a mistake. Fix it by
> rounding to a *number* of pages, rather than an order.
> 
> Until recently there was an even worse interaction with DMA_DIRECT_REMAP
> where we could have ended up decrypting part of the next adjacent
> vmalloc area, only averted by no architecture actually supporting both
> configs at once. Don't ask how I found that one out...
> 
> CC: stable@vger.kernel.org
> Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Acked-by: David Rientjes <rientjes@google.com>

WARNING: multiple messages have this Message-ID (diff)
From: David Rientjes via iommu <iommu@lists.linux-foundation.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: thomas.lendacky@amd.com, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org, iommu@lists.linux-foundation.org,
	hch@lst.de
Subject: Re: [PATCH] dma-direct: Don't over-decrypt memory
Date: Sun, 22 May 2022 18:04:51 -0700 (PDT)	[thread overview]
Message-ID: <22439fa1-5f9b-1e54-3f39-649b116574e@google.com> (raw)
In-Reply-To: <796ddc256b8a3054cb0b2f43363613463fcf0d61.1653066613.git.robin.murphy@arm.com>

On Fri, 20 May 2022, Robin Murphy wrote:

> The original x86 sev_alloc() only called set_memory_decrypted() on
> memory returned by alloc_pages_node(), so the page order calculation
> fell out of that logic. However, the common dma-direct code has several
> potential allocators, not all of which are guaranteed to round up the
> underlying allocation to a power-of-two size, so carrying over that
> calculation for the encryption/decryption size was a mistake. Fix it by
> rounding to a *number* of pages, rather than an order.
> 
> Until recently there was an even worse interaction with DMA_DIRECT_REMAP
> where we could have ended up decrypting part of the next adjacent
> vmalloc area, only averted by no architecture actually supporting both
> configs at once. Don't ask how I found that one out...
> 
> CC: stable@vger.kernel.org
> Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

Acked-by: David Rientjes <rientjes@google.com>
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  parent reply	other threads:[~2022-05-23  1:04 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-20 17:10 [PATCH] dma-direct: Don't over-decrypt memory Robin Murphy
2022-05-20 17:10 ` Robin Murphy
2022-05-22 13:07 ` Christoph Hellwig
2022-05-22 13:07   ` Christoph Hellwig
2022-05-23  1:04 ` David Rientjes [this message]
2022-05-23  1:04   ` David Rientjes via iommu

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