patches/kernel/0125-locking-barriers-Add-implicit-smp_read_barrier_depen.patch

   1 From 8b7859c0d35e5047d60c5e241fa40104b9c96f39 Mon Sep 17 00:00:00 2001
   2 From: Will Deacon <will.deacon@arm.com>
   3 Date: Tue, 24 Oct 2017 11:22:47 +0100
   4 Subject: [PATCH 125/233] locking/barriers: Add implicit
   5  smp_read_barrier_depends() to READ_ONCE()
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 CVE-2017-5754
  11
  12 [ Note, this is a Git cherry-pick of the following commit:
  13
  14     76ebbe78f739 ("locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()")
  15
  16   ... for easier x86 PTI code testing and back-porting. ]
  17
  18 In preparation for the removal of lockless_dereference(), which is the
  19 same as READ_ONCE() on all architectures other than Alpha, add an
  20 implicit smp_read_barrier_depends() to READ_ONCE() so that it can be
  21 used to head dependency chains on all architectures.
  22
  23 Signed-off-by: Will Deacon <will.deacon@arm.com>
  24 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  25 Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  26 Cc: Peter Zijlstra <peterz@infradead.org>
  27 Cc: Thomas Gleixner <tglx@linutronix.de>
  28 Link: http://lkml.kernel.org/r/1508840570-22169-3-git-send-email-will.deacon@arm.com
  29 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  30 (cherry picked from commit c2bc66082e1048c7573d72e62f597bdc5ce13fea)
  31 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  32 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  33 (cherry picked from commit 6ef3d843f8f1a8b72ca83d4b1d457c2896278ccd)
  34 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  35 ---
  36  include/linux/compiler.h | 1 +
  37  1 file changed, 1 insertion(+)
  38
  39 diff --git a/include/linux/compiler.h b/include/linux/compiler.h
  40 index 043b60de041e..8af8814ebe7a 100644
  41 --- a/include/linux/compiler.h
  42 +++ b/include/linux/compiler.h
  43 @@ -314,6 +314,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
  44                 __read_once_size(&(x), __u.__c, sizeof(x));             \
  45         else                                                            \
  46                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
  47 +       smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
  48         __u.__val;                                                      \
  49  })
  50  #define READ_ONCE(x) __READ_ONCE(x, 1)
  51 --
  52 2.14.2
  53