* Re: extended bpf_send_signal_thread with argument [not found] <CACT4Y+a7UBQpAY4vwT8Od0JhwbwcDrbJXZ_ULpPfJZ42Ew-yCQ@mail.gmail.com> @ 2021-02-01 9:22 ` Peter Zijlstra 2021-02-01 9:42 ` Dmitry Vyukov 0 siblings, 1 reply; 3+ messages in thread From: Peter Zijlstra @ 2021-02-01 9:22 UTC (permalink / raw) To: Dmitry Vyukov Cc: Steven Rostedt, Ingo Molnar, Alexei Starovoitov, Daniel Borkmann, andrii, Martin KaFai Lau, David Miller, kpsingh, John Fastabend, netdev, bpf, LKML 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. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: extended bpf_send_signal_thread with argument 2021-02-01 9:22 ` extended bpf_send_signal_thread with argument Peter Zijlstra @ 2021-02-01 9:42 ` Dmitry Vyukov 2021-02-01 13:33 ` Peter Zijlstra 0 siblings, 1 reply; 3+ messages in thread From: Dmitry Vyukov @ 2021-02-01 9:42 UTC (permalink / raw) To: Peter Zijlstra Cc: Steven Rostedt, Ingo Molnar, Alexei Starovoitov, Daniel Borkmann, andrii, Martin KaFai Lau, David Miller, kpsingh, John Fastabend, netdev, bpf, LKML 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? ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: extended bpf_send_signal_thread with argument 2021-02-01 9:42 ` Dmitry Vyukov @ 2021-02-01 13:33 ` Peter Zijlstra 0 siblings, 0 replies; 3+ messages in thread From: Peter Zijlstra @ 2021-02-01 13:33 UTC (permalink / raw) To: Dmitry Vyukov Cc: Steven Rostedt, Ingo Molnar, Alexei Starovoitov, Daniel Borkmann, andrii, Martin KaFai Lau, David Miller, kpsingh, John Fastabend, netdev, bpf, LKML 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. ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-02-01 13:35 UTC | newest]
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2021-02-01 9:22 ` extended bpf_send_signal_thread with argument Peter Zijlstra
2021-02-01 9:42 ` Dmitry Vyukov
2021-02-01 13:33 ` Peter Zijlstra
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