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Mon, 07 Sep 2026 05:44:29 -0700 (PDT) From: Donggeun Yoo To: Steven Rostedt , Masami Hiramatsu Cc: Mathieu Desnoyers , Tom Zanussi , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, donggeunyoo.kernel@gmail.com Subject: [PATCH 1/2] tracing: hist: take the reference before publishing the named trigger Date: Mon, 7 Sep 2026 21:44:19 +0900 Message-ID: <20260907124420.607097-2-donggeunyoo.kernel@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260907124420.607097-1-donggeunyoo.kernel@gmail.com> References: <20260907124420.607097-1-donggeunyoo.kernel@gmail.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit event_hist_trigger_named_init() puts the trigger on the global named_triggers list and only then takes the reference on the trigger it shares its histogram with: data->ref++; save_named_trigger(data->named_data->name, data); ret = event_hist_trigger_init(data->named_data); if (ret < 0) { kfree(data->cmd_ops); data->cmd_ops = &trigger_hist_cmd; } return ret; event_hist_trigger_init() fails when alloc_hist_pad() cannot allocate, and nothing takes the trigger back off the list on the way out. event_hist_trigger_parse() frees it, and the next lookup by name reads the freed object: BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0 Read of size 8 at addr ffff888009346860 by task init/1 find_named_trigger+0xac/0xc0 hist_register_trigger+0xc1/0xa00 event_hist_trigger_parse+0x3146/0x6af0 event_trigger_write+0xce/0x160 Freed by task 67: kfree+0x154/0x420 trigger_kthread_fn+0xfd/0x160 Do the reference first and publish once it has succeeded, so that nothing which can fail runs after the trigger becomes findable. Reported-by: Sashiko AI Closes: https://lore.kernel.org/linux-trace-kernel/20260907092944.3950E1F00A3D@smtp.kernel.org/ Fixes: 7ab0fc61ce73 ("tracing: Move histogram trigger variables from stack to per CPU structure") Cc: stable@vger.kernel.org Signed-off-by: Donggeun Yoo --- kernel/trace/trace_events_hist.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 963e0d6b61fd..c6c04926bdf0 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -6383,17 +6383,18 @@ static int event_hist_trigger_named_init(struct event_trigger_data *data) { int ret; - data->ref++; - - save_named_trigger(data->named_data->name, data); - ret = event_hist_trigger_init(data->named_data); if (ret < 0) { kfree(data->cmd_ops); data->cmd_ops = &trigger_hist_cmd; + return ret; } - return ret; + data->ref++; + + save_named_trigger(data->named_data->name, data); + + return 0; } static void event_hist_trigger_named_free(struct event_trigger_data *data) base-commit: df2908090cda368b01ff43709f51890076c56157 -- 2.53.0