module: Fix NULL vs IS_ERR checking for module_get_next_page

The module_get_next_page() function return error pointers on error
instead of NULL.
Use IS_ERR() to check the return value to fix this.

Fixes: b1ae6dc4 ("module: add in-kernel support for decompressing")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>

kernel/module/decompress.c

@@ -114,8 +114,8 @@ static ssize_t module_gzip_decompress(struct load_info *info,
 	do {
 		struct page *page = module_get_next_page(info);
 
-		if (!page) {
-			retval = -ENOMEM;
+		if (IS_ERR(page)) {
+			retval = PTR_ERR(page);
 			goto out_inflate_end;
 		}
 
@@ -173,8 +173,8 @@ static ssize_t module_xz_decompress(struct load_info *info,
 	do {
 		struct page *page = module_get_next_page(info);
 
-		if (!page) {
-			retval = -ENOMEM;
+		if (IS_ERR(page)) {
+			retval = PTR_ERR(page);
 			goto out;
 		}