Re: [PATCH] tracing/kprobes: Check whether get_kretprobe() returns NULL in kretprobe_dispatcher()

[Daniel Borkmann]

On 5/31/22 12:00 AM, Steven Rostedt wrote:
> On May 30, 2022 9:33:23 PM GMT+02:00, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> > On 5/27/22 5:55 PM, Masami Hiramatsu (Google) wrote:
> > > From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> > >
> > > There is a small chance that get_kretprobe(ri) returns NULL in
> > > kretprobe_dispatcher() when another CPU unregisters the kretprobe
> > > right after __kretprobe_trampoline_handler().
> > >
> > > To avoid this issue, kretprobe_dispatcher() checks the get_kretprobe()
> > > return value again. And if it is NULL, it returns soon because that
> > > kretprobe is under unregistering process.
> > >
> > > This issue has been introduced when the kretprobe is decoupled
> > > from the struct kretprobe_instance by commit d741bf41d7c7
> > > ("kprobes: Remove kretprobe hash"). Before that commit, the
> > > struct kretprob_instance::rp directly points the kretprobe
> > > and it is never be NULL.
> > >
> > > Reported-by: Yonghong Song <yhs@xxxxxx>
> > > Fixes: d741bf41d7c7 ("kprobes: Remove kretprobe hash")
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> >
> > Steven, I presume you'll pick this fix up?
>
> I'm currently at Embedded/Kernel Recipes, but yeah, I'll take a look at it. (Just need to finish my slides first ;-)

Ok, thanks. If I don't hear back I presume you'll pick it up then.