queue-4.4/powerpc-64-use-barrier_nospec-in-syscall-entry.patch

   1 From foo@baz Mon 29 Apr 2019 11:38:37 AM CEST
   2 From: Michael Ellerman <mpe@ellerman.id.au>
   3 Date: Mon, 22 Apr 2019 00:20:14 +1000
   4 Subject: powerpc/64: Use barrier_nospec in syscall entry
   5 To: stable@vger.kernel.org, gregkh@linuxfoundation.org
   6 Cc: linuxppc-dev@ozlabs.org, diana.craciun@nxp.com, msuchanek@suse.de, npiggin@gmail.com, christophe.leroy@c-s.fr
   7 Message-ID: <20190421142037.21881-30-mpe@ellerman.id.au>
   8
   9 From: Michael Ellerman <mpe@ellerman.id.au>
  10
  11 commit 51973a815c6b46d7b23b68d6af371ad1c9d503ca upstream.
  12
  13 Our syscall entry is done in assembly so patch in an explicit
  14 barrier_nospec.
  15
  16 Based on a patch by Michal Suchanek.
  17
  18 Signed-off-by: Michal Suchanek <msuchanek@suse.de>
  19 Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
  20 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  21 ---
  22  arch/powerpc/kernel/entry_64.S |   10 ++++++++++
  23  1 file changed, 10 insertions(+)
  24
  25 --- a/arch/powerpc/kernel/entry_64.S
  26 +++ b/arch/powerpc/kernel/entry_64.S
  27 @@ -36,6 +36,7 @@
  28  #include <asm/hw_irq.h>
  29  #include <asm/context_tracking.h>
  30  #include <asm/tm.h>
  31 +#include <asm/barrier.h>
  32  #ifdef CONFIG_PPC_BOOK3S
  33  #include <asm/exception-64s.h>
  34  #else
  35 @@ -177,6 +178,15 @@ system_call:                       /* label this so stack tr
  36         clrldi  r8,r8,32
  37  15:
  38         slwi    r0,r0,4
  39 +
  40 +       barrier_nospec_asm
  41 +       /*
  42 +        * Prevent the load of the handler below (based on the user-passed
  43 +        * system call number) being speculatively executed until the test
  44 +        * against NR_syscalls and branch to .Lsyscall_enosys above has
  45 +        * committed.
  46 +        */
  47 +
  48         ldx     r12,r11,r0      /* Fetch system call handler [ptr] */
  49         mtctr   r12
  50         bctrl                   /* Call handler */