linux-kernel - Re: [PATCHv5 bpf-next 03/13] bpf: Add support for uprobe multi session attach

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <Zv1FdjGzPf4KhtzP@krava>
Date: Wed, 2 Oct 2024 15:07:02 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Jiri Olsa <olsajiri@...il.com>, Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
	Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...omium.org>,
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCHv5 bpf-next 03/13] bpf: Add support for uprobe multi
 session attach

On Tue, Oct 01, 2024 at 10:11:13AM -0700, Andrii Nakryiko wrote:
> On Tue, Oct 1, 2024 at 6:17 AM Jiri Olsa <olsajiri@...il.com> wrote:
> >
> > On Mon, Sep 30, 2024 at 02:36:08PM -0700, Andrii Nakryiko wrote:
> >
> > SNIP
> >
> > > >  struct bpf_uprobe_multi_link {
> > > > @@ -3248,9 +3260,13 @@ uprobe_multi_link_handler(struct uprobe_consumer *con, struct pt_regs *regs,
> > > >                           __u64 *data)
> > > >  {
> > > >         struct bpf_uprobe *uprobe;
> > > > +       int ret;
> > > >
> > > >         uprobe = container_of(con, struct bpf_uprobe, consumer);
> > > > -       return uprobe_prog_run(uprobe, instruction_pointer(regs), regs);
> > > > +       ret = uprobe_prog_run(uprobe, instruction_pointer(regs), regs);
> > > > +       if (uprobe->session)
> > > > +               return ret ? UPROBE_HANDLER_IGNORE : 0;
> > > > +       return ret;
> > >
> > > isn't this a bug that BPF program can return arbitrary value here and,
> > > e.g., request uprobe unregistration?
> > >
> > > Let's return 0, unless uprobe->session? (it would be good to move that
> > > into a separate patch with Fixes)
> >
> > yea there's no use case for uprobe multi user, so let's return
> > 0 as you suggest
> >
> > >
> > > >  }
> > > >
> > > >  static int
> > > > @@ -3260,6 +3276,12 @@ uprobe_multi_link_ret_handler(struct uprobe_consumer *con, unsigned long func, s
> > > >         struct bpf_uprobe *uprobe;
> > > >
> > > >         uprobe = container_of(con, struct bpf_uprobe, consumer);
> > > > +       /*
> > > > +        * There's chance we could get called with NULL data if we registered uprobe
> > > > +        * after it hit entry but before it hit return probe, just ignore it.
> > > > +        */
> > > > +       if (uprobe->session && !data)
> > > > +               return 0;
> > >
> > > why can't handle_uretprobe_chain() do this check instead? We know when
> > > we are dealing with session uprobe/uretprobe, so we can filter out
> > > these spurious calls, no?
> >
> > right, now that we decide session based on presence of both callbacks
> > we have that info in here handle_uretprobe_chain.. but let's still check
> > it for sanity and warn? like
> >
> >         if (WARN_ON_ONCE(uprobe->session && !data))
> 
> You mean to check this *additionally* in uprobe_multi_link_handler(),
> after core uprobe code already filtered that condition out? It won't
> hurt, but I'm not sure I see the point?

yes, it's cross subsytem call so just to be on safe side for future,
but I don't insist

jirka