Re: [PATCH AUTOSEL 5.0 152/262] x86/kprobes: Prohibit probing on IRQ handlers directly

[Masami Hiramatsu]

Hi Sasha,

Could you drop this?
This prevents probing too much functions, and we will drop it
from upstream. Anyway, commit a50480cb6d61 ("kprobes/x86: 
Blacklist non-attachable interrupt functions") fixes same issue.
So please pick it instead of this.

Thank you,

On Wed, 27 Mar 2019 14:00:07 -0400
Sasha Levin <sashal@xxxxxxxxxx> wrote:

> From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> 
> [ Upstream commit 0eae81dc9f026d899c70f3931bf3bca6d7aa6938 ]
> 
> 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>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> Cc: Andrea Righi <righi.andrea@xxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Link: http://lkml.kernel.org/r/154998796400.31052.8406236614820687840.stgit@devbox
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@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 4ba75afba527..a034cb808e7e 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -1028,6 +1028,13 @@ 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);
>  }
> -- 
> 2.19.1
> 


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>