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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47aa0f21543sm72331539f8f.35.2026.07.12.09.10.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Jul 2026 09:10:10 -0700 (PDT) From: David Carlier To: Steven Rostedt , Masami Hiramatsu Cc: Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, David Carlier Subject: [PATCH] tracing: Defer trigger private data frees past the grace period Date: Sun, 12 Jul 2026 17:10:06 +0100 Message-ID: <20260712161006.242797-1-devnexen@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Commit 61d445af0a7c ("tracing: Add bulk garbage collection of freeing event_trigger_data") made trigger_data_free() defer the kfree() of the event_trigger_data to a kthread that runs tracepoint_synchronize_unregister() before freeing. The .free callbacks that own satellite data kept freeing it synchronously right after calling trigger_data_free(), relying on the synchronize that used to run inline. With that synchronize now deferred, event_hist_trigger_free(), event_enable_trigger_free() and event_hist_trigger_named_free() free hist_data, enable_data and cmd_ops while a concurrent tracepoint handler can still dereference them through the list_del_rcu()'d trigger, causing a use-after-free. Add an optional free_private() callback to event_trigger_data, invoked by the free kthread after the grace period, and move the satellite frees into it. The event_mutex-requiring bookkeeping (remove_hist_vars(), unregister_field_var_hists()) stays synchronous; only the handler-visible memory free is deferred. Fixes: 61d445af0a7c ("tracing: Add bulk garbage collection of freeing event_trigger_data") Signed-off-by: David Carlier --- kernel/trace/trace.h | 1 + kernel/trace/trace_events_hist.c | 19 +++++++++++++------ kernel/trace/trace_events_trigger.c | 18 +++++++++++++++--- 3 files changed, 29 insertions(+), 9 deletions(-) diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 80fe152af1dd..f04598337060 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1941,6 +1941,7 @@ struct event_trigger_data { struct list_head named_list; struct event_trigger_data *named_data; struct llist_node llist; + void (*free_private)(struct event_trigger_data *data); }; /* Avoid typos */ diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 82ce492ab268..bc696e4bd695 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -6335,6 +6335,16 @@ static void unregister_field_var_hists(struct hist_trigger_data *hist_data) } } +static void hist_trigger_free_private(struct event_trigger_data *data) +{ + destroy_hist_data(data->private_data); +} + +static void hist_trigger_named_free_private(struct event_trigger_data *data) +{ + kfree(data->cmd_ops); +} + static void event_hist_trigger_free(struct event_trigger_data *data) { struct hist_trigger_data *hist_data = data->private_data; @@ -6347,13 +6357,12 @@ static void event_hist_trigger_free(struct event_trigger_data *data) if (data->name) del_named_trigger(data); - trigger_data_free(data); - remove_hist_vars(hist_data); unregister_field_var_hists(hist_data); - destroy_hist_data(hist_data); + data->free_private = hist_trigger_free_private; + trigger_data_free(data); } free_hist_pad(); } @@ -6384,11 +6393,9 @@ static void event_hist_trigger_named_free(struct event_trigger_data *data) data->ref--; if (!data->ref) { - struct event_command *cmd_ops = data->cmd_ops; - del_named_trigger(data); + data->free_private = hist_trigger_named_free_private; trigger_data_free(data); - kfree(cmd_ops); } } diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 655db2e82513..27c54da041b7 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -38,6 +38,13 @@ static void trigger_create_kthread_locked(void) } } +static void trigger_data_free_one(struct event_trigger_data * data) +{ + if (data->free_private) + data->free_private(data); + kfree(data); +} + static void trigger_data_free_queued_locked(void) { struct event_trigger_data *data, *tmp; @@ -52,7 +59,7 @@ static void trigger_data_free_queued_locked(void) tracepoint_synchronize_unregister(); llist_for_each_entry_safe(data, tmp, llnodes, llist) - kfree(data); + trigger_data_free_one(data); } /* Bulk garbage collection of event_trigger_data elements */ @@ -75,7 +82,7 @@ static int trigger_kthread_fn(void *ignore) tracepoint_synchronize_unregister(); llist_for_each_entry_safe(data, tmp, llnodes, llist) - kfree(data); + trigger_data_free_one(data); } return 0; @@ -1717,6 +1724,11 @@ int event_enable_trigger_print(struct seq_file *m, return 0; } +static void enable_trigger_free_private(struct event_trigger_data *data) +{ + kfree(data->private_data); +} + void event_enable_trigger_free(struct event_trigger_data *data) { struct enable_trigger_data *enable_data = data->private_data; @@ -1729,8 +1741,8 @@ void event_enable_trigger_free(struct event_trigger_data *data) /* Remove the SOFT_MODE flag */ trace_event_enable_disable(enable_data->file, 0, 1); trace_event_put_ref(enable_data->file->event_call); + data->free_private = enable_trigger_free_private; trigger_data_free(data); - kfree(enable_data); } } -- 2.53.0