Messages in this thread | | | Date | Tue, 16 May 2023 14:10:28 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH] bpf: reject blacklisted symbols in kprobe_multi to avoid recursive trap |
| |
On Tue, 16 May 2023 13:31:53 +0900 Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> On Sat, 13 May 2023 00:17:57 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > On Fri, 12 May 2023 07:29:02 -0700 > > Yonghong Song <yhs@meta.com> wrote: > > > > > A fprobe_blacklist might make sense indeed as fprobe and kprobe are > > > quite different... Thanks for working on this. > > > > Hmm, I think I see the problem: > > > > fprobe_kprobe_handler() { > > kprobe_busy_begin() { > > preempt_disable() { > > preempt_count_add() { <-- trace > > fprobe_kprobe_handler() { > > [ wash, rinse, repeat, CRASH!!! ] > > > > Either the kprobe_busy_begin() needs to use preempt_disable_notrace() > > versions, or fprobe_kprobe_handle() needs a > > ftrace_test_recursion_trylock() call. > > Oops, I got it. Is preempt_count_add() tracable? If so, kprobe_busy_begin() > should be updated.
OK, preempt_count_add() is NOKPROBE_SYMBOL() so kprobe_busy_begin() should be safe. The problem is in fprobe_kprobe_handler() then.
Thanks!
> > Thanks, > > > > > -- Steve > > > -- > Masami Hiramatsu (Google) <mhiramat@kernel.org>
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
| |