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Wed, 15 Oct 2025 11:44:51 -0700 (PDT) Received: from 861G6M3 ([2a09:bac1:76a0:540::281:e4]) by smtp.gmail.com with ESMTPSA id 5614622812f47-441987494ccsm4180825b6e.0.2025.10.15.11.44.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Oct 2025 11:44:50 -0700 (PDT) Date: Wed, 15 Oct 2025 13:44:49 -0500 From: Chris Arges To: stable@vger.kernel.org Cc: kernel-team@cloudflare.com, Peter Zijlstra , David Wang <00107082@163.com>, Yeoreum Yun Subject: Re: [PATCH] perf: Fix dangling cgroup pointer in cpuctx Message-ID: References: <20251007164556.516406-1-carges@cloudflare.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251007164556.516406-1-carges@cloudflare.com> On 2025-10-07 11:45:52, Chris J Arges wrote: > From: Yeoreum Yun > > [ Upstream commit 3b7a34aebbdf2a4b7295205bf0c654294283ec82 ] > > Commit a3c3c66670ce ("perf/core: Fix child_total_time_enabled accounting > bug at task exit") moves the event->state update to before > list_del_event(). This makes the event->state test in list_del_event() > always false; never calling perf_cgroup_event_disable(). > > As a result, cpuctx->cgrp won't be cleared properly; causing havoc. > > Cc: stable@vger.kernel.org # 6.6.x, 6.12.x > Fixes: a3c3c66670ce ("perf/core: Fix child_total_time_enabled accounting bug at task exit") > Signed-off-by: Chris J Arges > --- > kernel/events/core.c | 21 ++++++--------------- > 1 file changed, 6 insertions(+), 15 deletions(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 3cc06ffb60c1..6688660845d2 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -2100,18 +2100,6 @@ list_del_event(struct perf_event *event, struct perf_event_context *ctx) > if (event->group_leader == event) > del_event_from_groups(event, ctx); > > - /* > - * If event was in error state, then keep it > - * that way, otherwise bogus counts will be > - * returned on read(). The only way to get out > - * of error state is by explicit re-enabling > - * of the event > - */ > - if (event->state > PERF_EVENT_STATE_OFF) { > - perf_cgroup_event_disable(event, ctx); > - perf_event_set_state(event, PERF_EVENT_STATE_OFF); > - } > - > ctx->generation++; > event->pmu_ctx->nr_events--; > } > @@ -2456,11 +2444,14 @@ __perf_remove_from_context(struct perf_event *event, > */ > if (flags & DETACH_EXIT) > state = PERF_EVENT_STATE_EXIT; > - if (flags & DETACH_DEAD) { > - event->pending_disable = 1; > + if (flags & DETACH_DEAD) > state = PERF_EVENT_STATE_DEAD; > - } > + > event_sched_out(event, ctx); > + > + if (event->state > PERF_EVENT_STATE_OFF) > + perf_cgroup_event_disable(event, ctx); > + > perf_event_set_state(event, min(event->state, state)); > if (flags & DETACH_GROUP) > perf_group_detach(event); > -- > 2.43.0 > Hi, can this patch be applied to stable 6.6.x and 6.12.x? Thanks, --chris