From: Lepton Wu <ytht.net@gmail.com>
Date: Tue, 16 Jan 2018 14:19:14 +0000 (+0100)
Subject: kaiser: Set _PAGE_NX only if supported
X-Git-Tag: v3.2.99~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d663ef5a8632389b31c629ac14485ca6f50a7f5e;p=thirdparty%2Fkernel%2Fstable.git

kaiser: Set _PAGE_NX only if supported

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>
---

diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c
index 8c95caecd3301..b6c645ec4906a 100644
--- a/arch/x86/mm/kaiser.c
+++ b/arch/x86/mm/kaiser.c
@@ -189,6 +189,8 @@ 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;
 
 	if (flags & _PAGE_USER)
 		BUG_ON(address < FIXADDR_START || end_addr >= FIXADDR_TOP);