staging: gasket: page_table: handle failed dma_map_page

Handle dma_map_page failing in gasket_alloc_extended_subtable: free
memory, don't add invalid page table entry.
Signed-off-by: Nick Ewalt <nicholasewalt@google.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gasket/gasket_page_table.c

@@ -902,6 +902,17 @@ static int gasket_alloc_extended_subtable(struct gasket_page_table *pg_tbl,
 	/* Map the page into DMA space. */
 	pte->dma_addr = dma_map_page(pg_tbl->device, pte->page, 0, PAGE_SIZE,
 				     DMA_TO_DEVICE);
+	if (dma_mapping_error(pg_tbl->device, pte->dma_addr)) {
+		dev_dbg(pg_tbl->device,
+			"%s: fail to map page [pfn %lx phys %llx]\n",
+			__func__, page_to_pfn(pte->page),
+			page_to_phys(pte->page));
+
+		free_page(page_addr);
+		vfree(pte->sublevel);
+		memset(pte, 0, sizeof(struct gasket_page_table_entry));
+		return -ENOMEM;
+	}
 
 	/* make the addresses available to the device */
 	dma_addr = (pte->dma_addr + pte->offset) | GASKET_VALID_SLOT_FLAG;