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[76.150.86.52]) by smtp.gmail.com with ESMTPSA id e9e14a558f8ab-430d07ccc89sm49925505ab.40.2025.10.21.21.25.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Oct 2025 21:25:23 -0700 (PDT) From: Yuhao Jiang To: "Rafael J . Wysocki" Cc: Len Brown , Hans de Goede , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yuhao Jiang Subject: [PATCH v2] ACPI: video: Fix use-after-free in acpi_video_switch_brightness() Date: Tue, 21 Oct 2025 23:25:14 -0500 Message-Id: <20251022042514.2167599-1-danisjiang@gmail.com> X-Mailer: git-send-email 2.34.1 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" The switch_brightness_work delayed work accesses device->brightness and device->backlight, which are freed by acpi_video_dev_unregister_backlight() during device removal. If the work executes after acpi_video_bus_unregister_backlight() frees these resources, it causes a use-after-free when acpi_video_switch_brightness() dereferences device->brightness or device->backlight. Fix this by calling cancel_delayed_work_sync() for each device's switch_brightness_work before unregistering its backlight resources. This ensures the work completes before the memory is freed. Fixes: 8ab58e8e7e097 ("ACPI / video: Fix backlight taking 2 steps on a brig= htness up/down keypress") Cc: stable@vger.kernel.org Signed-off-by: Yuhao Jiang --- Changes in v2: - Move cancel_delayed_work_sync() to acpi_video_bus_unregister_backlight() instead of acpi_video_bus_put_devices() for better logic clarity and to prevent potential UAF of device->brightness - Correct Fixes tag to point to 8ab58e8e7e097 which introduced the delayed = work - Link to v1: https://lore.kernel.org/all/20251022040859.2102914-1-danisjia= ng@gmail.com --- drivers/acpi/acpi_video.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c index 103f29661576..64709658bdc4 100644 --- a/drivers/acpi/acpi_video.c +++ b/drivers/acpi/acpi_video.c @@ -1869,8 +1869,10 @@ static int acpi_video_bus_unregister_backlight(struc= t acpi_video_bus *video) error =3D unregister_pm_notifier(&video->pm_nb); =20 mutex_lock(&video->device_list_lock); - list_for_each_entry(dev, &video->video_device_list, entry) + list_for_each_entry(dev, &video->video_device_list, entry) { + cancel_delayed_work_sync(&dev->switch_brightness_work); acpi_video_dev_unregister_backlight(dev); + } mutex_unlock(&video->device_list_lock); =20 video->backlight_registered =3D false; --=20 2.34.1