linux-kernel - [PATCH 13/19] perf: Robustify perf_event_free_bpf

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Message-Id: <20241104135518.978956692@infradead.org>
Date: Mon, 04 Nov 2024 14:39:22 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: mingo@...nel.org,
 lucas.demarchi@...el.com
Cc: linux-kernel@...r.kernel.org,
 peterz@...radead.org,
 willy@...radead.org,
 acme@...nel.org,
 namhyung@...nel.org,
 mark.rutland@....com,
 alexander.shishkin@...ux.intel.com,
 jolsa@...nel.org,
 irogers@...gle.com,
 adrian.hunter@...el.com,
 kan.liang@...ux.intel.com
Subject: [PATCH 13/19] perf: 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.

XXX perf_event_detach_bpf_prog() might leave a stale event->prog

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c |   19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10782,6 +10781,9 @@ int perf_event_set_bpf_prog(struct perf_
 
 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;