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 8c95cae..b6c645e 100644 (file)
--- 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);