x86/mpx: Do not allow MPX if we have mappings above 47-bit
MPX (without MAWA extension) cannot handle addresses above 47 bits, so we
need to make sure that MPX cannot be enabled if we already have a VMA above
the boundary and forbid creating such VMAs once MPX is enabled.
The patch implements mpx_unmapped_area_check() which is called from all
variants of get_unmapped_area() to check if the requested address fits
mpx.
On enabling MPX, we check if we already have any vma above 47-bit
boundary and forbit the enabling if we do.
As long as DEFAULT_MAP_WINDOW is equal to TASK_SIZE_MAX, the change is
nop. It will change when we allow userspace to have mappings above
47-bits.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170716225954.74185-6-kirill.shutemov@linux.intel.com
[ Readability edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index 868f02c..3cf89ad 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -18,6 +18,7 @@
#include <asm/tlbflush.h>
#include <asm/pgalloc.h>
#include <asm/elf.h>
+#include <asm/mpx.h>
#if 0 /* This is just for testing */
struct page *
@@ -135,6 +136,11 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
if (len & ~huge_page_mask(h))
return -EINVAL;
+
+ addr = mpx_unmapped_area_check(addr, len, flags);
+ if (IS_ERR_VALUE(addr))
+ return addr;
+
if (len > TASK_SIZE)
return -ENOMEM;