[tip: perf/core] perf/bpf: Robustify perf_event_free_bpf_prog()

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     c5b96789575b670b1e776071bb243e0ed3d3abaa
Gitweb:        https://git.kernel.org/tip/c5b96789575b670b1e776071bb243e0ed3d3abaa
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Mon, 04 Nov 2024 14:39:22 +01:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 04 Mar 2025 09:42:59 +01:00

perf/bpf: Robustify perf_event_free_bpf_prog()

Ensure perf_event_free_bpf_prog() is safe to call a second time;
notably without making any references to event->pmu when there is no
prog left.

Note: perf_event_detach_bpf_prog() might leave a stale event->prog

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241104135518.978956692@xxxxxxxxxxxxx
---
 kernel/events/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 525c64e..ab4e497 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10905,6 +10905,9 @@ int perf_event_set_bpf_prog(struct perf_event *event, struct bpf_prog *prog,
 
 void perf_event_free_bpf_prog(struct perf_event *event)
 {
+	if (!event->prog)
+		return;
+
 	if (!perf_event_is_tracing(event)) {
 		perf_event_free_bpf_handler(event);
 		return;