On Wed, Jul 19, 2023 at 7:08 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > now task-1 and task-2 share same bpf_trace_nest_level value and same > 'struct perf_sample_data' buffer on top of &sds->sds[1] > > I did not figure out yet the actual exact scenario/cause of the crash yet, > I suspect one of the tasks copies data over some boundary, but all the > ideas I had so far did not match the instructions from the crash > > anyway I thought that having 2 tasks sharing the same perf_sample_data > is bad enough to send the patch It makes sense now. We forgot to update this part during transition from preempt_disable to migrate_disable. But do you have PREEMPT_RCU in your kernel? If not then the above race shouldn't be possible. Worth fixing anyway, of course. Can you repro with a crafted test? Multiple uprobes doing bpf_perf_event_output should be enough, right? For kprobes we're "lucky" due to bpf_prog_active.
