Re: [PATCH v3] kprobes: Forbid probing on trampoline and bpf prog

Chen Zhongjin
2022-08-02T12:28:49Z

On 2022/8/2 17:06, Jiri Olsa wrote:
> On Mon, Aug 01, 2022 at 04:51:46PM -0400, Steven Rostedt wrote:
>> On Mon, 1 Aug 2022 22:41:19 +0200
>> Jiri Olsa <olsajiri@gmail.com> wrote:
>>
>>> LGTM cc-ing Steven because it affects ftrace as well
>> Thanks for the Cc, but I don't quite see how it affects ftrace.
>>
>> Unless you are just saying how it can affect kprobe_events?
> nope, I just saw the 'ftrace' in changelog ;-)
>
> anyway the patch makes check_kprobe_address_safe to fail
> on ftrace trampoline address.. but not sure you could make
> kprobe on ftrace trampoline before, probably not
>
> jirka

In fact with CONFIG_KPROBE_EVENTS_ON_NOTRACE=y it can happen.

But I think ftrace has no responsibility to promise the address safety
when this option open.

Best,

Chen

>> -- Steve
>>
>>
>>> jirka
>>>
>>>> v1 -> v2:
>>>> Check core_kernel_text and is_module_text_address rather than
>>>> only kprobe_insn.
>>>> Also fix title and commit message for this. See old patch at [1].
>>>> ---
>>>> kernel/kprobes.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
>>>> index f214f8c088ed..80697e5e03e4 100644
>>>> --- a/kernel/kprobes.c
>>>> +++ b/kernel/kprobes.c
>>>> @@ -1560,7 +1560,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
>>>> preempt_disable();
>>>>
>>>> /* Ensure it is not in reserved area nor out of text */
>>>> - if (!kernel_text_address((unsigned long) p->addr) ||
>>>> + if (!(core_kernel_text((unsigned long) p->addr) ||
>>>> + is_module_text_address((unsigned long) p->addr)) ||
>>>> within_kprobe_blacklist((unsigned long) p->addr) ||
>>>> jump_label_text_reserved(p->addr, p->addr) ||
>>>> static_call_text_reserved(p->addr, p->addr) ||
>>>> --
>>>> 2.17.1
>>>>