dma-direct: don't over-decrypt memory
authorRobin Murphy <robin.murphy@arm.com>
Fri, 20 May 2022 17:10:13 +0000 (18:10 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 9 Jun 2022 08:23:03 +0000 (10:23 +0200)
commita48a7f89494f5335f9e7a799ba9de68c1948f671
tree8845ee814abca861d17081dc94ad2acda3f2850d
parent5beb74d11eabd745d75bc91947b2721d2bd95deb
dma-direct: don't over-decrypt memory

[ 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@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
kernel/dma/direct.c