queue-4.19/arm64-backtrace-don-t-bother-trying-to-unwind-the-userspace-stack.patch

   1 From 1e6f5440a6814d28c32d347f338bfef68bc3e69d Mon Sep 17 00:00:00 2001
   2 From: Will Deacon <will.deacon@arm.com>
   3 Date: Mon, 8 Apr 2019 17:56:34 +0100
   4 Subject: arm64: backtrace: Don't bother trying to unwind the userspace stack
   5
   6 From: Will Deacon <will.deacon@arm.com>
   7
   8 commit 1e6f5440a6814d28c32d347f338bfef68bc3e69d upstream.
   9
  10 Calling dump_backtrace() with a pt_regs argument corresponding to
  11 userspace doesn't make any sense and our unwinder will simply print
  12 "Call trace:" before unwinding the stack looking for user frames.
  13
  14 Rather than go through this song and dance, just return early if we're
  15 passed a user register state.
  16
  17 Cc: <stable@vger.kernel.org>
  18 Fixes: 1149aad10b1e ("arm64: Add dump_backtrace() in show_regs")
  19 Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
  20 Signed-off-by: Will Deacon <will.deacon@arm.com>
  21 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  22
  23 ---
  24  arch/arm64/kernel/traps.c |   15 +++++++++------
  25  1 file changed, 9 insertions(+), 6 deletions(-)
  26
  27 --- a/arch/arm64/kernel/traps.c
  28 +++ b/arch/arm64/kernel/traps.c
  29 @@ -101,10 +101,16 @@ static void dump_instr(const char *lvl,
  30  void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
  31  {
  32         struct stackframe frame;
  33 -       int skip;
  34 +       int skip = 0;
  35
  36         pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
  37
  38 +       if (regs) {
  39 +               if (user_mode(regs))
  40 +                       return;
  41 +               skip = 1;
  42 +       }
  43 +
  44         if (!tsk)
  45                 tsk = current;
  46
  47 @@ -125,7 +131,6 @@ void dump_backtrace(struct pt_regs *regs
  48         frame.graph = tsk->curr_ret_stack;
  49  #endif
  50
  51 -       skip = !!regs;
  52         printk("Call trace:\n");
  53         do {
  54                 /* skip until specified stack frame */
  55 @@ -175,15 +180,13 @@ static int __die(const char *str, int er
  56                 return ret;
  57
  58         print_modules();
  59 -       __show_regs(regs);
  60         pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
  61                  TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk),
  62                  end_of_stack(tsk));
  63 +       show_regs(regs);
  64
  65 -       if (!user_mode(regs)) {
  66 -               dump_backtrace(regs, tsk);
  67 +       if (!user_mode(regs))
  68                 dump_instr(KERN_EMERG, regs);
  69 -       }
  70
  71         return ret;
  72  }