[PATCH 4/9] x86/kprobes: Prohibit probing on IRQ handlers directly

[Masami Hiramatsu <mhiramat@xxxxxxxxxx>]

Prohibit probing on IRQ handlers in irqentry_text because
if it interrupts user mode, at that point we haven't changed
to kernel space yet and which eventually leads a double fault.
E.g.

 # echo p apic_timer_interrupt > kprobe_events
 # echo 1 > events/kprobes/enable
 PANIC: double fault, error_code: 0x0
 CPU: 1 PID: 814 Comm: less Not tainted 4.20.0-rc3+ #30
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
 RIP: 0010:error_entry+0x12/0xf0
 [snip]
 Call Trace:
  <ENTRY_TRAMPOLINE>
  ? native_iret+0x7/0x7
  ? async_page_fault+0x8/0x30
  ? trace_hardirqs_on_thunk+0x1c/0x1c
  ? error_entry+0x7c/0xf0
  ? async_page_fault+0x8/0x30
  ? native_iret+0x7/0x7
  ? int3+0xa/0x20
  ? trace_hardirqs_on_thunk+0x1c/0x1c
  ? error_entry+0x7c/0xf0
  ? int3+0xa/0x20
  ? apic_timer_interrupt+0x1/0x20
  </ENTRY_TRAMPOLINE>
 Kernel panic - not syncing: Machine halted.
 Kernel Offset: disabled
 ---[ end Kernel panic - not syncing: Machine halted. ]---

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 arch/x86/kernel/kprobes/core.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index f4b954ff5b89..fed46ddb1eef 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1072,6 +1072,13 @@ NOKPROBE_SYMBOL(kprobe_fault_handler);
 
 int __init arch_populate_kprobe_blacklist(void)
 {
+	int ret;
+
+	ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
+					 (unsigned long)__irqentry_text_end);
+	if (ret)
+		return ret;
+
 	return kprobe_add_area_blacklist((unsigned long)__entry_text_start,
 					 (unsigned long)__entry_text_end);
 }