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From: Peter Zijlstra <peterz@infradead.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	andrii@kernel.org, Martin KaFai Lau <kafai@fb.com>,
	David Miller <davem@davemloft.net>,
	kpsingh@kernel.org, John Fastabend <john.fastabend@gmail.com>,
	netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: extended bpf_send_signal_thread with argument
Date: Mon, 1 Feb 2021 14:33:46 +0100	[thread overview]
Message-ID: <YBgDOnhrYjByjdIb@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CACT4Y+Yq69nvj2KZUQrYqtyu+Low+jCCcH++U_vuiHkhezQHGw@mail.gmail.com>

On Mon, Feb 01, 2021 at 10:42:47AM +0100, Dmitry Vyukov wrote:
> On Mon, Feb 1, 2021 at 10:22 AM Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Sun, Jan 31, 2021 at 12:14:02PM +0100, Dmitry Vyukov wrote:
> > > Hi,
> > >
> > > I would like to send a signal from a bpf program invoked from a
> > > perf_event. There is:
> >
> > You can't. Sending signals requires sighand lock, and you're not allowed
> > to take locks from perf_event context.
> 
> 
> Then we just found a vulnerability because there is
> bpf_send_signal_thread which can be attached to perf and it passes the
> verifier :)
> https://elixir.bootlin.com/linux/v5.11-rc5/source/kernel/trace/bpf_trace.c#L1145
> 
> It can defer sending the signal to the exit of irq context:
> https://elixir.bootlin.com/linux/v5.11-rc5/source/kernel/trace/bpf_trace.c#L1108
> Perhaps this is what makes it work?

Yes.

      reply	other threads:[~2021-02-01 13:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-31 11:14 extended bpf_send_signal_thread with argument Dmitry Vyukov
2021-02-01  9:22 ` Peter Zijlstra
2021-02-01  9:42   ` Dmitry Vyukov
2021-02-01 13:33     ` Peter Zijlstra [this message]

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