[PATCH 5.7 123/265] dma-direct: check return value when encrypting or decrypting memory

Sasha Levin
2020-06-29T22:00:45Z

From: David Rientjes <rientjes@google.com>

[ Upstream commit 56fccf21d1961a06e2a0c96ce446ebf036651062 ]

__change_page_attr() can fail which will cause set_memory_encrypted() and
set_memory_decrypted() to return non-zero.

If the device requires unencrypted DMA memory and decryption fails, simply
free the memory and fail.

If attempting to re-encrypt in the failure path and that encryption fails,
there is no alternative other than to leak the memory.

Fixes: c10f07aa27da ("dma/direct: Handle force decryption for DMA coherent buffers in common code")
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/dma/direct.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 4e789c46ff0bf..98c445dcb308b 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -124,6 +124,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
{
struct page *page;
void *ret;
+ int err;

if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
dma_alloc_need_uncached(dev, attrs) &&
@@ -176,8 +177,12 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
}

ret = page_address(page);
- if (force_dma_unencrypted(dev))
- set_memory_decrypted((unsigned long)ret, 1 << get_order(size));
+ if (force_dma_unencrypted(dev)) {
+ err = set_memory_decrypted((unsigned long)ret,
+ 1 << get_order(size));
+ if (err)
+ goto out_free_pages;
+ }

memset(ret, 0, size);

@@ -196,9 +201,13 @@ done:
return ret;

out_encrypt_pages:
- if (force_dma_unencrypted(dev))
- set_memory_encrypted((unsigned long)page_address(page),
- 1 << get_order(size));
+ if (force_dma_unencrypted(dev)) {
+ err = set_memory_encrypted((unsigned long)page_address(page),
+ 1 << get_order(size));
+ /* If memory cannot be re-encrypted, it must be leaked */
+ if (err)
+ return NULL;
+ }
out_free_pages:
dma_free_contiguous(dev, page, size);
return NULL;
--
2.25.1