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

[Chen Zhongjin]

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@xxxxxxxxx> 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
> > > >