bpf: Fail PERF_EVENT_IOC_SET_BPF when bpf_get_[stack|stackid] cannot work

[linux-2.6-microblaze.git] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 856d98c..ddcfd2f 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9544,6 +9544,24 @@ static int perf_event_set_bpf_handler(struct perf_event *event, u32 prog_fd)
        if (IS_ERR(prog))
                return PTR_ERR(prog);
 
+       if (event->attr.precise_ip &&
+           prog->call_get_stack &&
+           (!(event->attr.sample_type & __PERF_SAMPLE_CALLCHAIN_EARLY) ||
+            event->attr.exclude_callchain_kernel ||
+            event->attr.exclude_callchain_user)) {
+               /*
+                * On perf_event with precise_ip, calling bpf_get_stack()
+                * may trigger unwinder warnings and occasional crashes.
+                * bpf_get_[stack|stackid] works around this issue by using
+                * callchain attached to perf_sample_data. If the
+                * perf_event does not full (kernel and user) callchain
+                * attached to perf_sample_data, do not allow attaching BPF
+                * program that calls bpf_get_[stack|stackid].
+                */
+               bpf_prog_put(prog);
+               return -EPROTO;
+       }
+
        event->prog = prog;
        event->orig_overflow_handler = READ_ONCE(event->overflow_handler);
        WRITE_ONCE(event->overflow_handler, bpf_overflow_handler);