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: sta...@vger.kernel.org
> Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent
> buffers in common code")
> Signed-off-by: Robin Murphy <robin.mur...@arm.com>
Acked-by: David Rientjes <rient...@google.com>
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