[tip:x86/vdso] x86/vdso: Set VM_MAYREAD for the vvar vma

[tip-bot for Andy Lutomirski <tipbot@zytor.com>]

Commit-ID:  ac379835e820de27429b5c4eadf4c1b40320cff4
Gitweb:     http://git.kernel.org/tip/ac379835e820de27429b5c4eadf4c1b40320cff4
Author:     Andy Lutomirski <luto@amacapital.net>
AuthorDate: Fri, 25 Jul 2014 16:27:01 -0700
Committer:  H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Fri, 25 Jul 2014 16:32:53 -0700

x86/vdso: Set VM_MAYREAD for the vvar vma

The VVAR area can, obviously, be read; that is kind of the point.

AFAIK this has no effect whatsoever unless x86 suddenly turns into a
nommu architecture.  Nonetheless, not setting it is suspicious.

Reported-by: Nathan Lynch <Nathan_Lynch@mentor.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/e4c8bf4bc2725bda22c4a4b7d0c82adcd8f8d9b8.1406330779.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/vdso/vma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
index dbef622..970463b 100644
--- a/arch/x86/vdso/vma.c
+++ b/arch/x86/vdso/vma.c
@@ -138,7 +138,7 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 	vma = _install_special_mapping(mm,
 				       addr,
 				       -image->sym_vvar_start,
-				       VM_READ,
+				       VM_READ|VM_MAYREAD,
 				       &vvar_mapping);
 
 	if (IS_ERR(vma)) {