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([46.110.19.170]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8949183272csm105024566d6.13.2026.01.26.18.36.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Jan 2026 18:36:37 -0800 (PST) From: Henry Zhang X-Google-Original-From: Henry Zhang To: peterz@infradead.org, mingo@redhat.com Cc: acme@kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Henry Zhang , syzbot+2a077cb788749964cf68@syzkaller.appspotmail.com Subject: [PATCH] perf: Fix data race in perf_event_set_bpf_handler() Date: Mon, 26 Jan 2026 21:36:18 -0500 Message-Id: <20260127023618.1469937-1-zeri@umich.edu> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" KCSAN reported a data race where perf_event_set_bpf_handler() writes event->prog while __perf_event_overflow() reads it concurrently from interrupt context: BUG: KCSAN: data-race in __perf_event_overflow / __perf_event_set_bpf_prog write to 0xffff88811b219168 of 8 bytes by task 13065 on cpu 0: perf_event_set_bpf_handler kernel/events/core.c:10352 [inline] __perf_event_set_bpf_prog+0x418/0x470 kernel/events/core.c:11303 ... read to 0xffff88811b219168 of 8 bytes by interrupt on cpu 1: __perf_event_overflow+0x252/0x920 kernel/events/core.c:10410 ... Annotate event->prog access with WRITE_ONCE/READ_ONCE. Reported-by: syzbot+2a077cb788749964cf68@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D2a077cb788749964cf68 Signed-off-by: Henry Zhang --- kernel/events/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index a0fa488bce84..1f3ed9e87507 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10349,7 +10349,7 @@ static inline int perf_event_set_bpf_handler(struct= perf_event *event, return -EPROTO; } =20 - event->prog =3D prog; + WRITE_ONCE(event->prog, prog); event->bpf_cookie =3D bpf_cookie; return 0; } @@ -10407,7 +10407,9 @@ static int __perf_event_overflow(struct perf_event = *event, if (event->attr.aux_pause) perf_event_aux_pause(event->aux_event, true); =20 - if (event->prog && event->prog->type =3D=3D BPF_PROG_TYPE_PERF_EVENT && + struct bpf_prog *prog =3D READ_ONCE(event->prog); + + if (prog && prog->type =3D=3D BPF_PROG_TYPE_PERF_EVENT && !bpf_overflow_handler(event, data, regs)) goto out; =20 --=20 2.34.1