Peter reported that perf_event_detach_bpf_prog might skip to release
the bpf program for -ENOENT error from bpf_prog_array_copy.
This can't happen because bpf program is stored in perf event and is
detached and released only when perf event is freed.
Let's make it obvious and add WARN_ON_ONCE on the -ENOENT check and
make sure the bpf program is released in any case.
Cc: Sean Young <sean@xxxxxxxx>
Fixes: 170a7e3ea070 ("bpf: bpf_prog_array_copy() should return -ENOENT if exclude_prog not found")
Closes: https://lore.kernel.org/lkml/20241022111638.GC16066@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
kernel/trace/bpf_trace.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 95b6b3b16bac..2c064ba7b0bd 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2216,8 +2216,8 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
old_array = bpf_event_rcu_dereference(event->tp_event->prog_array);
ret = bpf_prog_array_copy(old_array, event->prog, NULL, 0, &new_array);
- if (ret == -ENOENT)
- goto unlock;
+ if (WARN_ON_ONCE(ret == -ENOENT))
+ goto put;
if (ret < 0) {
bpf_prog_array_delete_safe(old_array, event->prog);
} else {
@@ -2225,6 +2225,7 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
bpf_prog_array_free_sleepable(old_array);
}
+put:
bpf_prog_put(event->prog);
event->prog = NULL;
--
2.46.2
