dma-direct: check return value when encrypting or decrypting memory

__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: c10f07aa ("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>

kernel/dma/direct.c

@@ -158,6 +158,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 {
 	struct page *page;
 	void *ret;
+	int err;
 
 	size = PAGE_ALIGN(size);
 
@@ -210,8 +211,12 @@ 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);
 
@@ -230,9 +235,13 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 	return ret;
 
 out_encrypt_pages:
-	if (force_dma_unencrypted(dev))
-		set_memory_encrypted((unsigned long)page_address(page),
+	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;