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bh=w3/Au2kP5Om3EOJLFjtCzhhmhbbdbQyveovhkztCay4=; b=fGY8JdZF1qG9CKmaZRoMe/p42g8wbharSNM4HP9PvUxQfxVuA6Ixo2xhvPkZ0NaHS0h67p T4a4vlWxB9xdd5A2IABssx2pTQEk8PO+QWJn+1FC6jlitiI7pJ62q9MKi7BTaKpkWV7TrO pq+btCWOkGzhahDHXZac9xxI2jNeC2LM6bwIwmBVUs4b+ErIPu4UiXeMgSr292tKNO8Ztm kIGT7FArrUGsEZUE6v1owGuNp+Q8L9OzVm4cQcr7/h+nuPzW8OqDWAqQPbaEK8FpJUjbJp RHpVRvhEfBSPvmvMACmwT/qqYo3pJolYfGFO0DOrzgBX1dXRG0mPyqu289oX/Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1771936613; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w3/Au2kP5Om3EOJLFjtCzhhmhbbdbQyveovhkztCay4=; b=wyJFgHdWZPgX8H1kO9EWFR+TGDbPHKmuisP+Q/DRskhEXPoyF62G7ibiiebZDzdX1xykMe 2ryHK6LwZsqQGVAQ== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: perf/urgent] perf: Fix data race in perf_event_set_bpf_handler() Cc: "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20260224122909.GV1395416@noisy.programming.kicks-ass.net> References: <20260224122909.GV1395416@noisy.programming.kicks-ass.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <177193661171.1647592.9395163829843540847.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the perf/urgent branch of tip: Commit-ID: 5004d5c59874b18c8ecbcb507053750c8b47353c Gitweb: https://git.kernel.org/tip/5004d5c59874b18c8ecbcb507053750c8= b47353c Author: Peter Zijlstra AuthorDate: Tue, 24 Feb 2026 13:29:09 +01:00 Committer: Peter Zijlstra CommitterDate: Tue, 24 Feb 2026 13:33:39 +01:00 perf: Fix data race in perf_event_set_bpf_handler() On Fri, Jan 30, 2026 at 11:07:33AM +0100, Peter Zijlstra wrote: > On Tue, Jan 27, 2026 at 04:37:19PM +0800, Qing Wang wrote: > > On Tue, 27 Jan 2026 at 10:36, Henry Zhang wr= ote: > > > 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; > > > } > > > > > > - 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); > > > > > > - if (event->prog && event->prog->type =3D=3D BPF_PROG_TYPE_PERF_EVEN= T && > > > + 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; > > > > Looking at this code, I guess there may be an serious issue: a potential > > use-after-free (UAF) risk when accessing event->prog in __perf_event_ov= erflow. > > > > CPU 0 (interrupt context) CPU 1 (process context) > > read event->prog > > perf_event_free_bpf_handler() > > put(prog) > > free(prog) > > access memory pointed to by prog > > > > This scenario need to be more analysis. > > This can only happen if the event can overlap with removal, which it > typically cannot -- but I'll have to audit the software events. > > Specifically, events happen in IRQ/NMI context, and event removal > involves an IPI to that very CPU, which by necessity will then have to > wait for event completion. Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260224122909.GV1395416@noisy.programming.k= icks-ass.net --- kernel/events/core.c | 42 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 22a0f40..1f5699b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -10777,6 +10777,13 @@ int perf_event_overflow(struct perf_event *event, struct perf_sample_data *data, struct pt_regs *regs) { + /* + * Entry point from hardware PMI, interrupts should be disabled here. + * This serializes us against perf_event_remove_from_context() in + * things like perf_event_release_kernel(). + */ + lockdep_assert_irqs_disabled(); + return __perf_event_overflow(event, 1, data, regs); } =20 @@ -10853,6 +10860,19 @@ static void perf_swevent_event(struct perf_event *= event, u64 nr, { struct hw_perf_event *hwc =3D &event->hw; =20 + /* + * This is: + * - software preempt + * - tracepoint preempt + * - tp_target_task irq (ctx->lock) + * - uprobes preempt/irq + * - kprobes preempt/irq + * - hw_breakpoint irq + * + * Any of these are sufficient to hold off RCU and thus ensure @event + * exists. + */ + lockdep_assert_preemption_disabled(); local64_add(nr, &event->count); =20 if (!regs) @@ -10861,6 +10881,16 @@ static void perf_swevent_event(struct perf_event *= event, u64 nr, if (!is_sampling_event(event)) return; =20 + /* + * Serialize against event_function_call() IPIs like normal overflow + * event handling. Specifically, must not allow + * perf_event_release_kernel() -> perf_remove_from_context() to make + * progress and 'release' the event from under us. + */ + guard(irqsave)(); + if (event->state !=3D PERF_EVENT_STATE_ACTIVE) + return; + if ((event->attr.sample_type & PERF_SAMPLE_PERIOD) && !event->attr.freq) { data->period =3D nr; return perf_swevent_overflow(event, 1, data, regs); @@ -11359,6 +11389,11 @@ void perf_tp_event(u16 event_type, u64 count, void= *record, int entry_size, struct perf_sample_data data; struct perf_event *event; =20 + /* + * Per being a tracepoint, this runs with preemption disabled. + */ + lockdep_assert_preemption_disabled(); + struct perf_raw_record raw =3D { .frag =3D { .size =3D entry_size, @@ -11691,6 +11726,11 @@ void perf_bp_event(struct perf_event *bp, void *da= ta) struct perf_sample_data sample; struct pt_regs *regs =3D data; =20 + /* + * Exception context, will have interrupts disabled. + */ + lockdep_assert_irqs_disabled(); + perf_sample_data_init(&sample, bp->attr.bp_addr, 0); =20 if (!bp->hw.state && !perf_exclude_event(bp, regs)) @@ -12155,7 +12195,7 @@ static enum hrtimer_restart perf_swevent_hrtimer(st= ruct hrtimer *hrtimer) =20 if (regs && !perf_exclude_event(event, regs)) { if (!(event->attr.exclude_idle && is_idle_task(current))) - if (__perf_event_overflow(event, 1, &data, regs)) + if (perf_event_overflow(event, &data, regs)) ret =3D HRTIMER_NORESTART; } =20