patches/kernel/0137-x86-entry-64-paravirt-Use-paravirt-safe-macro-to-acc.patch

   1 From a76244535c7a04fde0afa6971ee1ecdb8d5b0c22 Mon Sep 17 00:00:00 2001
   2 From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
   3 Date: Mon, 4 Dec 2017 15:07:07 +0100
   4 Subject: [PATCH 137/233] x86/entry/64/paravirt: Use paravirt-safe macro to
   5  access eflags
   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 Commit 1d3e53e8624a ("x86/entry/64: Refactor IRQ stacks and make them
  13 NMI-safe") added DEBUG_ENTRY_ASSERT_IRQS_OFF macro that acceses eflags
  14 using 'pushfq' instruction when testing for IF bit. On PV Xen guests
  15 looking at IF flag directly will always see it set, resulting in 'ud2'.
  16
  17 Introduce SAVE_FLAGS() macro that will use appropriate save_fl pv op when
  18 running paravirt.
  19
  20 Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
  21 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  22 Reviewed-by: Juergen Gross <jgross@suse.com>
  23 Cc: Andy Lutomirski <luto@kernel.org>
  24 Cc: Borislav Petkov <bp@alien8.de>
  25 Cc: Borislav Petkov <bpetkov@suse.de>
  26 Cc: Brian Gerst <brgerst@gmail.com>
  27 Cc: Dave Hansen <dave.hansen@intel.com>
  28 Cc: Dave Hansen <dave.hansen@linux.intel.com>
  29 Cc: David Laight <David.Laight@aculab.com>
  30 Cc: Denys Vlasenko <dvlasenk@redhat.com>
  31 Cc: Eduardo Valentin <eduval@amazon.com>
  32 Cc: Greg KH <gregkh@linuxfoundation.org>
  33 Cc: H. Peter Anvin <hpa@zytor.com>
  34 Cc: Josh Poimboeuf <jpoimboe@redhat.com>
  35 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  36 Cc: Peter Zijlstra <peterz@infradead.org>
  37 Cc: Rik van Riel <riel@redhat.com>
  38 Cc: Will Deacon <will.deacon@arm.com>
  39 Cc: aliguori@amazon.com
  40 Cc: daniel.gruss@iaik.tugraz.at
  41 Cc: hughd@google.com
  42 Cc: keescook@google.com
  43 Cc: xen-devel@lists.xenproject.org
  44 Link: https://lkml.kernel.org/r/20171204150604.899457242@linutronix.de
  45 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  46 (cherry picked from commit e17f8234538d1ff708673f287a42457c4dee720d)
  47 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  48 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  49 (cherry picked from commit 9f4a274842938ce8d55565ced4f45e7ad4a5da90)
  50 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  51 ---
  52  arch/x86/include/asm/irqflags.h  | 3 +++
  53  arch/x86/include/asm/paravirt.h  | 9 +++++++++
  54  arch/x86/kernel/asm-offsets_64.c | 3 +++
  55  arch/x86/entry/entry_64.S        | 7 ++++---
  56  4 files changed, 19 insertions(+), 3 deletions(-)
  57
  58 diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
  59 index ac7692dcfa2e..d937781e1047 100644
  60 --- a/arch/x86/include/asm/irqflags.h
  61 +++ b/arch/x86/include/asm/irqflags.h
  62 @@ -141,6 +141,9 @@ static inline notrace unsigned long arch_local_irq_save(void)
  63         swapgs;                                 \
  64         sysretl
  65
  66 +#ifdef CONFIG_DEBUG_ENTRY
  67 +#define SAVE_FLAGS(x)          pushfq; popq %rax
  68 +#endif
  69  #else
  70  #define INTERRUPT_RETURN               iret
  71  #define ENABLE_INTERRUPTS_SYSEXIT      sti; sysexit
  72 diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
  73 index 43d4f90edebc..52dcd2361a78 100644
  74 --- a/arch/x86/include/asm/paravirt.h
  75 +++ b/arch/x86/include/asm/paravirt.h
  76 @@ -926,6 +926,15 @@ extern void default_banner(void);
  77         PARA_SITE(PARA_PATCH(pv_cpu_ops, PV_CPU_usergs_sysret64),       \
  78                   CLBR_NONE,                                            \
  79                   jmp PARA_INDIRECT(pv_cpu_ops+PV_CPU_usergs_sysret64))
  80 +
  81 +#ifdef CONFIG_DEBUG_ENTRY
  82 +#define SAVE_FLAGS(clobbers)                                        \
  83 +       PARA_SITE(PARA_PATCH(pv_irq_ops, PV_IRQ_save_fl), clobbers, \
  84 +                 PV_SAVE_REGS(clobbers | CLBR_CALLEE_SAVE);        \
  85 +                 call PARA_INDIRECT(pv_irq_ops+PV_IRQ_save_fl);    \
  86 +                 PV_RESTORE_REGS(clobbers | CLBR_CALLEE_SAVE);)
  87 +#endif
  88 +
  89  #endif /* CONFIG_X86_32 */
  90
  91  #endif /* __ASSEMBLY__ */
  92 diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
  93 index cf42206926af..c21a5315b38e 100644
  94 --- a/arch/x86/kernel/asm-offsets_64.c
  95 +++ b/arch/x86/kernel/asm-offsets_64.c
  96 @@ -22,6 +22,9 @@ int main(void)
  97  #ifdef CONFIG_PARAVIRT
  98         OFFSET(PV_CPU_usergs_sysret64, pv_cpu_ops, usergs_sysret64);
  99         OFFSET(PV_CPU_swapgs, pv_cpu_ops, swapgs);
 100 +#ifdef CONFIG_DEBUG_ENTRY
 101 +       OFFSET(PV_IRQ_save_fl, pv_irq_ops, save_fl);
 102 +#endif
 103         BLANK();
 104  #endif
 105
 106 diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
 107 index 2491b3b25b9a..6c73e96daf78 100644
 108 --- a/arch/x86/entry/entry_64.S
 109 +++ b/arch/x86/entry/entry_64.S
 110 @@ -461,12 +461,13 @@ END(irq_entries_start)
 111
 112  .macro DEBUG_ENTRY_ASSERT_IRQS_OFF
 113  #ifdef CONFIG_DEBUG_ENTRY
 114 -       pushfq
 115 -       testl $X86_EFLAGS_IF, (%rsp)
 116 +       pushq %rax
 117 +       SAVE_FLAGS(CLBR_RAX)
 118 +       testl $X86_EFLAGS_IF, %eax
 119         jz .Lokay_\@
 120         ud2
 121  .Lokay_\@:
 122 -       addq $8, %rsp
 123 +       popq %rax
 124  #endif
 125  .endm
 126
 127 --
 128 2.14.2
 129