patches/kernel/0088-x86-entry-64-Remove-the-restore_c_regs_and_iret-labe.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Andy Lutomirski <luto@kernel.org>
   3 Date: Thu, 2 Nov 2017 00:58:58 -0700
   4 Subject: [PATCH] x86/entry/64: Remove the restore_c_regs_and_iret label
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 CVE-2017-5754
  10
  11 The only user was the 64-bit opportunistic SYSRET failure path, and
  12 that path didn't really need it.  This change makes the
  13 opportunistic SYSRET code a bit more straightforward and gets rid of
  14 the label.
  15
  16 Signed-off-by: Andy Lutomirski <luto@kernel.org>
  17 Reviewed-by: Borislav Petkov <bp@suse.de>
  18 Cc: Borislav Petkov <bpetkov@suse.de>
  19 Cc: Brian Gerst <brgerst@gmail.com>
  20 Cc: Dave Hansen <dave.hansen@intel.com>
  21 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  22 Cc: Peter Zijlstra <peterz@infradead.org>
  23 Cc: Thomas Gleixner <tglx@linutronix.de>
  24 Link: http://lkml.kernel.org/r/be3006a7ad3326e3458cf1cc55d416252cbe1986.1509609304.git.luto@kernel.org
  25 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  26 (cherry picked from commit 9da78ba6b47b46428cfdfc0851511ab29c869798)
  27 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  28 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  29 (cherry picked from commit 629c8b858cbe72e88e7f44a8f10e1b434ab80721)
  30 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  31 ---
  32  arch/x86/entry/entry_64.S | 5 ++---
  33  1 file changed, 2 insertions(+), 3 deletions(-)
  34
  35 diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
  36 index 34adfe0221d2..fac354ddf056 100644
  37 --- a/arch/x86/entry/entry_64.S
  38 +++ b/arch/x86/entry/entry_64.S
  39 @@ -245,7 +245,6 @@ entry_SYSCALL64_slow_path:
  40         call    do_syscall_64           /* returns with IRQs disabled */
  41
  42  return_from_SYSCALL_64:
  43 -       RESTORE_EXTRA_REGS
  44         TRACE_IRQS_IRETQ                /* we're about to change IF */
  45
  46         /*
  47 @@ -314,6 +313,7 @@ return_from_SYSCALL_64:
  48          */
  49  syscall_return_via_sysret:
  50         /* rcx and r11 are already restored (see code above) */
  51 +       RESTORE_EXTRA_REGS
  52         RESTORE_C_REGS_EXCEPT_RCX_R11
  53         movq    RSP(%rsp), %rsp
  54         UNWIND_HINT_EMPTY
  55 @@ -321,7 +321,7 @@ syscall_return_via_sysret:
  56
  57  opportunistic_sysret_failed:
  58         SWAPGS
  59 -       jmp     restore_c_regs_and_iret
  60 +       jmp     restore_regs_and_iret
  61  END(entry_SYSCALL_64)
  62
  63  ENTRY(stub_ptregs_64)
  64 @@ -638,7 +638,6 @@ retint_kernel:
  65   */
  66  GLOBAL(restore_regs_and_iret)
  67         RESTORE_EXTRA_REGS
  68 -restore_c_regs_and_iret:
  69         RESTORE_C_REGS
  70         REMOVE_PT_GPREGS_FROM_STACK 8
  71         INTERRUPT_RETURN
  72 --
  73 2.14.2
  74