Messages in this thread | | | From | Dmitry Vyukov <> | Date | Mon, 1 Feb 2021 10:42:47 +0100 | Subject | Re: extended bpf_send_signal_thread with argument |
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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?
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