From nobody Thu Apr 2 17:10:50 2026 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 0E1BF3D9045; Fri, 27 Mar 2026 09:49:55 +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=1774604996; cv=none; b=uuGZAA53w8m/BWTu1wKjNzjScGpGFA+QPkwfB/9REZBcYT18ALnXsaqt9e6SCY8zgKjXwai5V+3IwZ1ia97SizrYT7sA/JYuOyYg3v1ByBvYEgG/VFMgCDrXehyl2h8VJ4slXij7wSojgDyCpDKAzzJKrPaMwm37K74wAnuLyXU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774604996; c=relaxed/simple; bh=V9D/je/3dq/FkNs/GXhMLrcWvkhQNHNDQGhW2GWmafk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=sypcuITksFpxYSeLuKZZw1L8da/x85Hg1WbJIdl8w9DMU3cBjbMz3uxlqmeBKwgDgOjbnJccwC72vBKz1k0LkAKwoycX7ISlgLNvhIbBW9DXMcGDSe0DttNVlACk+h25BSc+Mt3gAcnHut7CY1cFwF22JPXF9DzXRgnO6iWsVts= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e0W59P6l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="e0W59P6l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D23FC19424; Fri, 27 Mar 2026 09:49:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774604995; bh=V9D/je/3dq/FkNs/GXhMLrcWvkhQNHNDQGhW2GWmafk=; h=From:To:Cc:Subject:Date:From; b=e0W59P6lb71lp6LCvQpgWaCA3tIclv4s2CnIsWVUGacV+9OQkz98hx3bf2XzR2DHg c5fjJQolr2n1xFmDRtKhIy0e1iKxSa7ajFEHrbS9k1vneFdVyZQ8grYshEwp2OgLKs iUnrcXn3/H3d9jXrl+kxVGgm2HZWrko+08SGoc30TIxzuKFK/z0WWaEItySInpEpHm Efa+BWthuo3fJlZbX4/RtqDC2Bh0+cYBb5pTAVKD0FleZE5/dtZlbOe6LKMHe+Ztf9 dsv4mvKuigQlyFYzIDyEa8sp/IRNLOsshwj9xKxBby3CeqYBdfCFEGcHW7XhAfG8Ao YWSACzxsxJ3UQ== From: "Rafael J. Wysocki" To: Linux PM , Daniel Lezcano , Lukasz Luba Cc: Mauricio Faria de Oliveira , LKML Subject: [PATCH v2] thermal: core: Address thermal zone removal races with resume Date: Fri, 27 Mar 2026 10:49:52 +0100 Message-ID: <6267615.lOV4Wx5bFT@rafael.j.wysocki> Organization: Linux Kernel Development 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" From: Rafael J. Wysocki Since thermal_zone_pm_complete() and thermal_zone_device_resume() re-initialize the poll_queue delayed work for the given thermal zone, the cancel_delayed_work_sync() in thermal_zone_device_unregister() may miss some already running work items and the thermal zone may be freed prematurely [1]. There are two failing scenarios that both start with running thermal_pm_notify_complete() right before invoking thermal_zone_device_unregister() for one of the thermal zones. In the first scenario, there is a work item already running for the given thermal zone when thermal_pm_notify_complete() calls thermal_zone_pm_complete() for that thermal zone and it continues to run when thermal_zone_device_unregister() starts. Since the poll_queue delayed work has been re-initialized by thermal_pm_notify_complete(), the running work item will be missed by the cancel_delayed_work_sync() in thermal_zone_device_unregister() and if it continues to run past the freeing of the thermal zone object, a use-after-free will occur. In the second scenario, thermal_zone_device_resume() queued up by thermal_pm_notify_complete() runs right after the thermal_zone_exit() called by thermal_zone_device_unregister() has returned. The poll_queue delayed work is re-initialized by it before cancel_delayed_work_sync() is called by thermal_zone_device_unregister(), so it may continue to run after the freeing of the thermal zone object, which also leads to a use-after-free. Address the first failing scenario by ensuring that no thermal work items will be running when thermal_pm_notify_complete() is called. For this purpose, first move the cancel_delayed_work() call from thermal_zone_pm_complete() to thermal_zone_pm_prepare() to prevent new work from entering the workqueue going forward. Next, switch over to using a dedicated workqueue for thermal events and update the code in thermal_pm_notify() to flush that workqueue after thermal_pm_notify_prepare() has returned which will take care of all leftover thermal work already on the workqueue (that leftover work would do nothing useful anyway because all of the thermal zones have been flagged as suspended). The second failing scenario is addressed by adding a tz->state check to thermal_zone_device_resume() to prevent it from re-initializing the poll_queue delayed work if the thermal zone is going away. Note that the above changes will also facilitate relocating the suspend and resume of thermal zones closer to the suspend and resume of devices, respectively. Fixes: 5a5efdaffda5 ("thermal: core: Resume thermal zones asynchronously") Reported-by: Mauricio Faria de Oliveira Closes: https://lore.kernel.org/linux-pm/20260324-thermal-core-uaf-init_del= ayed_work-v1-1-6611ae76a8a1@igalia.com/ [1] Signed-off-by: Rafael J. Wysocki Reported-by: syzbot+3b3852c6031d0f30dfaf@syzkaller.appspotmail.com Reviewed-by: Lukasz Luba Reviewed-by: Mauricio Faria de Oliveira Tested-by: Mauricio Faria de Oliveira --- v1 -> v2: Return -ENOMEM from thermal_init() when the workqueue allocation fails (Sashiko) Lukasz, Daniel, I'm quite confident about this patch, but I would appreciate your feedback. --- drivers/thermal/thermal_core.c | 31 ++++++++++++++++++++++++++----- 1 file changed, 26 insertions(+), 5 deletions(-) --- a/drivers/thermal/thermal_core.c +++ b/drivers/thermal/thermal_core.c @@ -42,6 +42,8 @@ static struct thermal_governor *def_gove =20 static bool thermal_pm_suspended; =20 +static struct workqueue_struct *thermal_wq __ro_after_init; + /* * Governor section: set of functions to handle thermal governors * @@ -314,7 +316,7 @@ static void thermal_zone_device_set_poll if (delay > HZ) delay =3D round_jiffies_relative(delay); =20 - mod_delayed_work(system_freezable_power_efficient_wq, &tz->poll_queue, de= lay); + mod_delayed_work(thermal_wq, &tz->poll_queue, delay); } =20 static void thermal_zone_recheck(struct thermal_zone_device *tz, int error) @@ -1795,6 +1797,10 @@ static void thermal_zone_device_resume(s =20 guard(thermal_zone)(tz); =20 + /* If the thermal zone is going away, there's nothing to do. */ + if (tz->state & TZ_STATE_FLAG_EXIT) + return; + tz->state &=3D ~(TZ_STATE_FLAG_SUSPENDED | TZ_STATE_FLAG_RESUMING); =20 thermal_debug_tz_resume(tz); @@ -1825,6 +1831,9 @@ static void thermal_zone_pm_prepare(stru } =20 tz->state |=3D TZ_STATE_FLAG_SUSPENDED; + + /* Prevent new work from getting to the workqueue subsequently. */ + cancel_delayed_work(&tz->poll_queue); } =20 static void thermal_pm_notify_prepare(void) @@ -1843,8 +1852,6 @@ static void thermal_zone_pm_complete(str { guard(thermal_zone)(tz); =20 - cancel_delayed_work(&tz->poll_queue); - reinit_completion(&tz->resume); tz->state |=3D TZ_STATE_FLAG_RESUMING; =20 @@ -1854,7 +1861,7 @@ static void thermal_zone_pm_complete(str */ INIT_DELAYED_WORK(&tz->poll_queue, thermal_zone_device_resume); /* Queue up the work without a delay. */ - mod_delayed_work(system_freezable_power_efficient_wq, &tz->poll_queue, 0); + mod_delayed_work(thermal_wq, &tz->poll_queue, 0); } =20 static void thermal_pm_notify_complete(void) @@ -1877,6 +1884,11 @@ static int thermal_pm_notify(struct noti case PM_RESTORE_PREPARE: case PM_SUSPEND_PREPARE: thermal_pm_notify_prepare(); + /* + * Allow any leftover thermal work items already on the + * worqueue to complete so they don't get in the way later. + */ + flush_workqueue(thermal_wq); break; case PM_POST_HIBERNATION: case PM_POST_RESTORE: @@ -1909,9 +1921,16 @@ static int __init thermal_init(void) if (result) goto error; =20 + thermal_wq =3D alloc_workqueue("thermal_events", + WQ_FREEZABLE | WQ_POWER_EFFICIENT | WQ_PERCPU, 0); + if (!thermal_wq) { + result =3D -ENOMEM; + goto unregister_netlink; + } + result =3D thermal_register_governors(); if (result) - goto unregister_netlink; + goto destroy_workqueue; =20 thermal_class =3D kzalloc_obj(*thermal_class); if (!thermal_class) { @@ -1938,6 +1957,8 @@ static int __init thermal_init(void) =20 unregister_governors: thermal_unregister_governors(); +destroy_workqueue: + destroy_workqueue(thermal_wq); unregister_netlink: thermal_netlink_exit(); error: