patches/kernel/0090-x86-entry-64-Shrink-paranoid_exit_restore-and-make-l.patch

   1 From d8fdea47d7fc1177aa0843a49dc89422ac6f4fea Mon Sep 17 00:00:00 2001
   2 From: Andy Lutomirski <luto@kernel.org>
   3 Date: Thu, 2 Nov 2017 00:59:02 -0700
   4 Subject: [PATCH 090/242] x86/entry/64: Shrink paranoid_exit_restore and make
   5  labels local
   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 paranoid_exit_restore was a copy of restore_regs_and_return_to_kernel.
  13 Merge them and make the paranoid_exit internal labels local.
  14
  15 Keeping .Lparanoid_exit makes the code a bit shorter because it
  16 allows a 2-byte jnz instead of a 5-byte jnz.
  17
  18 Saves 96 bytes of text.
  19
  20 ( This is still a bit suboptimal in a non-CONFIG_TRACE_IRQFLAGS
  21   kernel, but fixing that would make the code rather messy. )
  22
  23 Signed-off-by: Andy Lutomirski <luto@kernel.org>
  24 Cc: Borislav Petkov <bpetkov@suse.de>
  25 Cc: Brian Gerst <brgerst@gmail.com>
  26 Cc: Dave Hansen <dave.hansen@intel.com>
  27 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  28 Cc: Peter Zijlstra <peterz@infradead.org>
  29 Cc: Thomas Gleixner <tglx@linutronix.de>
  30 Link: http://lkml.kernel.org/r/510d66a1895cda9473c84b1086f0bb974f22de6a.1509609304.git.luto@kernel.org
  31 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  32 (cherry picked from commit e53178328c9b96fbdbc719e78c93b5687ee007c3)
  33 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  34 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  35 (cherry picked from commit fb53fe10add935c3d0eb63199e43426eaf3b4299)
  36 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  37 ---
  38  arch/x86/entry/entry_64.S | 13 +++++--------
  39  1 file changed, 5 insertions(+), 8 deletions(-)
  40
  41 diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
  42 index a1a86e782a0e..6995f7e08aa1 100644
  43 --- a/arch/x86/entry/entry_64.S
  44 +++ b/arch/x86/entry/entry_64.S
  45 @@ -1136,17 +1136,14 @@ ENTRY(paranoid_exit)
  46         DISABLE_INTERRUPTS(CLBR_ANY)
  47         TRACE_IRQS_OFF_DEBUG
  48         testl   %ebx, %ebx                      /* swapgs needed? */
  49 -       jnz     paranoid_exit_no_swapgs
  50 +       jnz     .Lparanoid_exit_no_swapgs
  51         TRACE_IRQS_IRETQ
  52         SWAPGS_UNSAFE_STACK
  53 -       jmp     paranoid_exit_restore
  54 -paranoid_exit_no_swapgs:
  55 +       jmp     .Lparanoid_exit_restore
  56 +.Lparanoid_exit_no_swapgs:
  57         TRACE_IRQS_IRETQ_DEBUG
  58 -paranoid_exit_restore:
  59 -       RESTORE_EXTRA_REGS
  60 -       RESTORE_C_REGS
  61 -       REMOVE_PT_GPREGS_FROM_STACK 8
  62 -       INTERRUPT_RETURN
  63 +.Lparanoid_exit_restore:
  64 +       jmp restore_regs_and_return_to_kernel
  65  END(paranoid_exit)
  66
  67  /*
  68 --
  69 2.14.2
  70