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Sat, 05 Apr 2025 13:30:42 -0700 (PDT) Received: from theriatric.mshome.net ([73.123.232.110]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c76e96e566sm384878985a.63.2025.04.05.13.30.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 05 Apr 2025 13:30:42 -0700 (PDT) From: Gabriel Shahrouzi To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , linux-perf-users@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Ian Rogers , Adrian Hunter , Kan Liang , Shuah Khan , linux-kernel-mentees@lists.linux.dev, Gustavo Shahrouzi , syzkaller-bugs@googlegroups.com, syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com Subject: [PATCH] perf/core: Prevent WARN_ON(!ctx) in __free_event for partial init Date: Sat, 5 Apr 2025 16:30:36 -0400 Message-ID: <20250405203036.582721-1-gshahrouzi@gmail.com> X-Mailer: git-send-email 2.43.0 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" Move the get_ctx(child_ctx) call and the child_event->ctx assignment to occur immediately after the child event is allocated. Ensure that child_event->ctx is non-NULL before any subsequent error path within inherit_event calls free_event(), satisfying the assumptions of the cleanup code. Reported-by: syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Dff3aa851d46ab82953a3 Signed-off-by: Gabriel Shahrouzi --- kernel/events/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 0bb21659e252..153ba622cfa0 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -14016,6 +14016,9 @@ inherit_event(struct perf_event *parent_event, if (IS_ERR(child_event)) return child_event; =20 + get_ctx(child_ctx); + child_event->ctx =3D child_ctx; + pmu_ctx =3D find_get_pmu_context(child_event->pmu, child_ctx, child_event= ); if (IS_ERR(pmu_ctx)) { free_event(child_event); @@ -14037,8 +14040,6 @@ inherit_event(struct perf_event *parent_event, return NULL; } =20 - get_ctx(child_ctx); - /* * Make the child state follow the state of the parent event, * not its attr.disabled bit. We hold the parent's mutex, @@ -14059,7 +14060,6 @@ inherit_event(struct perf_event *parent_event, local64_set(&hwc->period_left, sample_period); } =20 - child_event->ctx =3D child_ctx; child_event->overflow_handler =3D parent_event->overflow_handler; child_event->overflow_handler_context =3D parent_event->overflow_handler_context; --=20 2.43.0