x86/pkeys: Add fault handling for PF_PK page fault bit

PF_PK means that a memory access violated the protection key
access restrictions.  It is unconditionally an access_error()
because the permissions set on the VMA don't matter (the PKRU
value overrides it), and we never "resolve" PK faults (like
how a COW can "resolve write fault).

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: linux-arch@vger.kernel.org
Cc: Dave Hansen <dave@sr71.net>
Cc: arnd@arndb.de
Cc: linux-api@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: luto@kernel.org
Cc: akpm@linux-foundation.org
Cc: torvalds@linux-foundation.org
Link: http://lkml.kernel.org/r/20160729163010.DD1FE1ED@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index dc80230..b88d8ac 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1112,6 +1112,15 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
 {
        /* This is only called for the current mm, so: */
        bool foreign = false;
+
+       /*
+        * Read or write was blocked by protection keys.  This is
+        * always an unconditional error and can never result in
+        * a follow-up action to resolve the fault, like a COW.
+        */
+       if (error_code & PF_PK)
+               return 1;
+
        /*
         * Make sure to check the VMA so that we do not perform
         * faults just to hit a PF_PK as soon as we fill in a