On Fri, Jun 17, 2022 at 01:46:49PM +0100, Robin Murphy wrote:
> [ Upstream commit 4a37f3dd9a83186cb88d44808ab35b78375082c9 ]
>
> 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...
>
> Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
> [ backport the functional change without all the prior refactoring ]
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> ---
>
> Hi Greg, Sasha,
>
> I see you managed to resolve this back as far as 5.15 already, so please
> consider this backport to complete the set. This may need to end up in
> the Android 5.10 kernel in future for unpleasant reasons, but as an
> upstream fix I figure it may as well take the upstream stable route too.
Now queued up, thanks.
greg k-h
