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@xxxxxxxxxxxxx> 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.
