linux-kernel - [tip: perf/core] perf/bpf: Robustify perf_event_free_bpf

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Message-ID: <174107862138.14745.820346394726926625.tip-bot2@tip-bot2>
Date: Tue, 04 Mar 2025 08:57:01 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>, Ravi Bangoria <ravi.bangoria@....com>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/bpf: Robustify perf_event_free_bpf_prog()

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@...radead.org>
AuthorDate:    Mon, 04 Nov 2024 14:39:22 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
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@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@....com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: Andrii Nakryiko <andrii@...nel.org>
Link: https://lore.kernel.org/r/20241104135518.978956692@infradead.org
---
 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;