[PATCH AUTOSEL 6.1 28/52] dma-direct: Leak pages on dma_set_decrypted() failure

Sasha Levin
2024-03-29T12:46:58Z

From: Rick Edgecombe <rick.p.edgecombe@intel.com>

[ Upstream commit b9fa16949d18e06bdf728a560f5c8af56d2bdcaf ]

On TDX it is possible for the untrusted host to cause
set_memory_encrypted() or set_memory_decrypted() to fail such that an
error is returned and the resulting memory is shared. Callers need to
take care to handle these errors to avoid returning decrypted (shared)
memory to the page allocator, which could lead to functional or security
issues.

DMA could free decrypted/shared pages if dma_set_decrypted() fails. This
should be a rare case. Just leak the pages in this case instead of
freeing them.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/dma/direct.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 63859a101ed83..d4215739efc71 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -296,7 +296,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
} else {
ret = page_address(page);
if (dma_set_decrypted(dev, ret, size))
- goto out_free_pages;
+ goto out_leak_pages;
}

memset(ret, 0, size);
@@ -317,6 +317,8 @@ void *dma_direct_alloc(struct device *dev, size_t size,
out_free_pages:
__dma_direct_free_pages(dev, page, size);
return NULL;
+out_leak_pages:
+ return NULL;
}

void dma_direct_free(struct device *dev, size_t size,
@@ -379,12 +381,11 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,

ret = page_address(page);
if (dma_set_decrypted(dev, ret, size))
- goto out_free_pages;
+ goto out_leak_pages;
memset(ret, 0, size);
*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
return page;
-out_free_pages:
- __dma_direct_free_pages(dev, page, size);
+out_leak_pages:
return NULL;
}

--
2.43.0