releases/4.19.34/arm64-debug-don-t-propagate-unknown-far-into-si_code-for-debug-signals.patch

   1 From b9a4b9d084d978f80eb9210727c81804588b42ff Mon Sep 17 00:00:00 2001
   2 From: Will Deacon <will.deacon@arm.com>
   3 Date: Fri, 1 Mar 2019 13:28:00 +0000
   4 Subject: arm64: debug: Don't propagate UNKNOWN FAR into si_code for debug signals
   5
   6 From: Will Deacon <will.deacon@arm.com>
   7
   8 commit b9a4b9d084d978f80eb9210727c81804588b42ff upstream.
   9
  10 FAR_EL1 is UNKNOWN for all debug exceptions other than those caused by
  11 taking a hardware watchpoint. Unfortunately, if a debug handler returns
  12 a non-zero value, then we will propagate the UNKNOWN FAR value to
  13 userspace via the si_addr field of the SIGTRAP siginfo_t.
  14
  15 Instead, let's set si_addr to take on the PC of the faulting instruction,
  16 which we have available in the current pt_regs.
  17
  18 Cc: <stable@vger.kernel.org>
  19 Reviewed-by: Mark Rutland <mark.rutland@arm.com>
  20 Signed-off-by: Will Deacon <will.deacon@arm.com>
  21 Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23
  24
  25 ---
  26  arch/arm64/mm/fault.c |    9 +++++----
  27  1 file changed, 5 insertions(+), 4 deletions(-)
  28
  29 --- a/arch/arm64/mm/fault.c
  30 +++ b/arch/arm64/mm/fault.c
  31 @@ -827,11 +827,12 @@ void __init hook_debug_fault_code(int nr
  32         debug_fault_info[nr].name       = name;
  33  }
  34
  35 -asmlinkage int __exception do_debug_exception(unsigned long addr,
  36 +asmlinkage int __exception do_debug_exception(unsigned long addr_if_watchpoint,
  37                                               unsigned int esr,
  38                                               struct pt_regs *regs)
  39  {
  40         const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr);
  41 +       unsigned long pc = instruction_pointer(regs);
  42         int rv;
  43
  44         /*
  45 @@ -841,10 +842,10 @@ asmlinkage int __exception do_debug_exce
  46         if (interrupts_enabled(regs))
  47                 trace_hardirqs_off();
  48
  49 -       if (user_mode(regs) && instruction_pointer(regs) > TASK_SIZE)
  50 +       if (user_mode(regs) && pc > TASK_SIZE)
  51                 arm64_apply_bp_hardening();
  52
  53 -       if (!inf->fn(addr, esr, regs)) {
  54 +       if (!inf->fn(addr_if_watchpoint, esr, regs)) {
  55                 rv = 1;
  56         } else {
  57                 struct siginfo info;
  58 @@ -853,7 +854,7 @@ asmlinkage int __exception do_debug_exce
  59                 info.si_signo = inf->sig;
  60                 info.si_errno = 0;
  61                 info.si_code  = inf->code;
  62 -               info.si_addr  = (void __user *)addr;
  63 +               info.si_addr  = (void __user *)pc;
  64                 arm64_notify_die(inf->name, regs, &info, esr);
  65                 rv = 0;
  66         }