[PATCH 3.2 79/79] kaiser: Set _PAGE_NX only if supported

Ben Hutchings
2018-02-11T04:20:06Z

From: 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

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Lepton Wu <ytht.net@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(backported from Greg K-H's 4.4 stable-queue)
Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/mm/kaiser.c | 2 ++
1 file changed, 2 insertions(+)

--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -189,6 +189,8 @@ static int kaiser_add_user_map(const voi
* 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;

if (flags & _PAGE_USER)
BUG_ON(address < FIXADDR_START || end_addr >= FIXADDR_TOP);