[PATCH 4.4-stable v3] kaiser: Set _PAGE_NX only if supported

[Lepton Wu <ytht.net@gmail.com>]

This finally resolve crash if loaded under qemu + haxm. Haitao Shan pointed
out that the reason of that crash is that NX bit get set for page tables.
It seems we missed checking if _PAGE_NX is supported in kaiser_add_user_map

Link: https://www.spinics.net/lists/kernel/msg2689835.html

Signed-off-by: Lepton Wu <ytht.net@gmail.com>
---
 arch/x86/mm/kaiser.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 6a7a77929a8c..8af98513d36c 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -198,6 +198,8 @@ static int kaiser_add_user_map(const void *__start_addr, unsigned long size,
 	 * requires that not to be #defined to 0): so mask it off here.
 	 */
 	flags &= ~_PAGE_GLOBAL;
+	if (!(__supported_pte_mask & _PAGE_NX))
+		flags &= ~_PAGE_NX;
 
 	for (; address < end_addr; address += PAGE_SIZE) {
 		target_address = get_pa_from_mapping(address);
-- 
2.16.0.rc1.238.g530d649a79-goog