x86/mm/ident_map: Check for errors from ident_pud_init()

Commit

  ea3b5e60 ("x86/mm/ident_map: Add 5-level paging support")

added ident_p4d_init() to support 5-level paging, but this function
doesn't check and return errors from ident_pud_init().

For example, the decompressor stub uses this code to create an identity
mapping. If it runs out of pages while trying to allocate a PMD
pagetable, the error will be currently ignored.

Fix this to propagate errors.

 [ bp: Space out statements for better readability. ]

Fixes: ea3b5e60 ("x86/mm/ident_map: Add 5-level paging support")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20201027230648.1885111-1-nivedita@alum.mit.edu

arch/x86/mm/ident_map.c

@@ -62,6 +62,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
 			  unsigned long addr, unsigned long end)
 {
 	unsigned long next;
+	int result;
 
 	for (; addr < end; addr = next) {
 		p4d_t *p4d = p4d_page + p4d_index(addr);
@@ -73,13 +74,20 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
 
 		if (p4d_present(*p4d)) {
 			pud = pud_offset(p4d, 0);
-			ident_pud_init(info, pud, addr, next);
+			result = ident_pud_init(info, pud, addr, next);
+			if (result)
+				return result;
+
 			continue;
 		}
 		pud = (pud_t *)info->alloc_pgt_page(info->context);
 		if (!pud)
 			return -ENOMEM;
-		ident_pud_init(info, pud, addr, next);
+
+		result = ident_pud_init(info, pud, addr, next);
+		if (result)
+			return result;
+
 		set_p4d(p4d, __p4d(__pa(pud) | info->kernpg_flag));
 	}