dma-direct: reject highmem pages from dma_alloc_from_contiguous

dma_alloc_from_contiguous can return highmem pages depending on the
setup, which a plain non-remapping DMA allocator can't handle.  Detect
this case and fail the allocation.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

kernel/dma/direct.c

@@ -162,6 +162,18 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
 	if (!page)
 		return NULL;
 
+	if (PageHighMem(page)) {
+		/*
+		 * Depending on the cma= arguments and per-arch setup
+		 * dma_alloc_from_contiguous could return highmem pages.
+		 * Without remapping there is no way to return them here,
+		 * so log an error and fail.
+		 */
+		dev_info(dev, "Rejecting highmem page from CMA.\n");
+		__dma_direct_free_pages(dev, size, page);
+		return NULL;
+	}
+
 	ret = page_address(page);
 	if (force_dma_unencrypted()) {
 		set_memory_decrypted((unsigned long)ret, 1 << get_order(size));