From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 19A5D426D2A; Tue, 31 Mar 2026 16:41:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774975260; cv=none; b=ZXjAOhboupJGtkuBkMUbCskyW2JKYkXAlC4eMcOOGWW5ox6RbpzR+hMchdqcj2HrI1DfR2eHKfz04HfTRCeJpxa96NExfyi3gCmVke0xBOJ15xOP6hrD/97tkiHxJl9MQI351Tj5jHhO1euv1A+mUj9S++8yKA7FUCPoVtCVlEc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774975260; c=relaxed/simple; bh=54hCqm564O39sQDIiUw0GT3NTKdwYweguemHkZyaouw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dzQ+4NcJqyLjoml9+0xUhnFqeXHrNJ7rJzY5sp9TO5hzCiRPmFm2TucH6595q28LuUJCV6LjrCXJtr5YxseeS1dvhxbTsNSB2aTmZYsBwhYPanqjghvDffKa40FcEEYeZjwtUknabMhbxitRNptwphEN9w2G3M2bL2ycSQgC9ZY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Fd0SoHhj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Fd0SoHhj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A361EC19423; Tue, 31 Mar 2026 16:40:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774975260; bh=54hCqm564O39sQDIiUw0GT3NTKdwYweguemHkZyaouw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Fd0SoHhj5EujMtxBd/RoCdqZjL8svWBSBV1msP+k4QmMk2cJ4/3OWH+B3Tzix5Ajb NPrh4OODxKGz4cr4bGBoBpxGY7safviWC2seNiX+lFR2AjHV/9v1Ve7z4lLDwXDsUa 4YZmoUp+UIlClScZ7Y79zPlqI9fCSu92dYhuN1og= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wesley Atwell , "Steven Rostedt (Google)" Subject: [PATCH 6.19 198/342] tracing: Drain deferred trigger frees if kthread creation fails Date: Tue, 31 Mar 2026 18:20:31 +0200 Message-ID: <20260331161806.275620893@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260331161758.909578033@linuxfoundation.org> References: <20260331161758.909578033@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wesley Atwell commit 250ab25391edeeab8462b68be42e4904506c409c upstream. Boot-time trigger registration can fail before the trigger-data cleanup kthread exists. Deferring those frees until late init is fine, but the post-boot fallback must still drain the deferred list if kthread creation never succeeds. Otherwise, boot-deferred nodes can accumulate on trigger_data_free_list, later frees fall back to synchronously freeing only the current object, and the older queued entries are leaked forever. To trigger this, add the following to the kernel command line: trace_event=sched_switch trace_trigger=sched_switch.traceon,sched_switch.traceon The second traceon trigger will fail and be freed. This triggers a NULL pointer dereference and crashes the kernel. Keep the deferred boot-time behavior, but when kthread creation fails, drain the whole queued list synchronously. Do the same in the late-init drain path so queued entries are not stranded there either. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260324221326.1395799-3-atwellwea@gmail.com Fixes: 61d445af0a7c ("tracing: Add bulk garbage collection of freeing event_trigger_data") Signed-off-by: Wesley Atwell Signed-off-by: Steven Rostedt (Google) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_trigger.c | 79 ++++++++++++++++++++++++++++++------ 1 file changed, 66 insertions(+), 13 deletions(-) --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -22,6 +22,39 @@ static struct task_struct *trigger_kthre static struct llist_head trigger_data_free_list; static DEFINE_MUTEX(trigger_data_kthread_mutex); +static int trigger_kthread_fn(void *ignore); + +static void trigger_create_kthread_locked(void) +{ + lockdep_assert_held(&trigger_data_kthread_mutex); + + if (!trigger_kthread) { + struct task_struct *kthread; + + kthread = kthread_create(trigger_kthread_fn, NULL, + "trigger_data_free"); + if (!IS_ERR(kthread)) + WRITE_ONCE(trigger_kthread, kthread); + } +} + +static void trigger_data_free_queued_locked(void) +{ + struct event_trigger_data *data, *tmp; + struct llist_node *llnodes; + + lockdep_assert_held(&trigger_data_kthread_mutex); + + llnodes = llist_del_all(&trigger_data_free_list); + if (!llnodes) + return; + + tracepoint_synchronize_unregister(); + + llist_for_each_entry_safe(data, tmp, llnodes, llist) + kfree(data); +} + /* Bulk garbage collection of event_trigger_data elements */ static int trigger_kthread_fn(void *ignore) { @@ -56,30 +89,50 @@ void trigger_data_free(struct event_trig if (data->cmd_ops->set_filter) data->cmd_ops->set_filter(NULL, data, NULL); + /* + * Boot-time trigger registration can fail before kthread creation + * works. Keep the deferred-free semantics during boot and let late + * init start the kthread to drain the list. + */ + if (system_state == SYSTEM_BOOTING && !trigger_kthread) { + llist_add(&data->llist, &trigger_data_free_list); + return; + } + if (unlikely(!trigger_kthread)) { guard(mutex)(&trigger_data_kthread_mutex); + + trigger_create_kthread_locked(); /* Check again after taking mutex */ if (!trigger_kthread) { - struct task_struct *kthread; - - kthread = kthread_create(trigger_kthread_fn, NULL, - "trigger_data_free"); - if (!IS_ERR(kthread)) - WRITE_ONCE(trigger_kthread, kthread); + llist_add(&data->llist, &trigger_data_free_list); + /* Drain the queued frees synchronously if creation failed. */ + trigger_data_free_queued_locked(); + return; } } - if (!trigger_kthread) { - /* Do it the slow way */ - tracepoint_synchronize_unregister(); - kfree(data); - return; - } - llist_add(&data->llist, &trigger_data_free_list); wake_up_process(trigger_kthread); } +static int __init trigger_data_free_init(void) +{ + guard(mutex)(&trigger_data_kthread_mutex); + + if (llist_empty(&trigger_data_free_list)) + return 0; + + trigger_create_kthread_locked(); + if (trigger_kthread) + wake_up_process(trigger_kthread); + else + trigger_data_free_queued_locked(); + + return 0; +} +late_initcall(trigger_data_free_init); + static inline void data_ops_trigger(struct event_trigger_data *data, struct trace_buffer *buffer, void *rec, struct ring_buffer_event *event)