[PATCH] x86/mm: avoid premature success when changing page attributes

[Jan Beulich]

Since successful return from __cpa_process_fault() makes
__change_page_attr() exit early (and successfully), its caller needs to
be instructed to continue its iteration by adjusting ->numpages. While
this already happens on one of __cpa_process_fault()'s successful exit
paths, the other needs this done similarly. This was in particular a
problem when the top level caller passed zero for "checkalias"
(becoming the "primary" value for the other two mentioned functions),
as is the case in change_page_attr_set_clr() when the OR of "mask_set"
and "mask_clr" equals _PAGE_NX, as e.g. passed from set_memory_{,n}x().

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 arch/x86/mm/pageattr.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- 4.5-rc1/arch/x86/mm/pageattr.c
+++ 4.5-rc1-x86-cpa-non-primary/arch/x86/mm/pageattr.c
@@ -1122,8 +1122,10 @@ static int __cpa_process_fault(struct cp
 	/*
 	 * Ignore all non primary paths.
 	 */
-	if (!primary)
+	if (!primary) {
+		cpa->numpages = 1;
 		return 0;
+	}
 
 	/*
 	 * Ignore the NULL PTE for kernel identity mapping, as it is expected