From: Oliver Neukum Date: Thu, 12 Sep 2024 12:32:59 +0000 (+0200) Subject: USB: appledisplay: close race between probe and completion handler X-Git-Tag: v6.12-rc1~42^2~4 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8265d06b7794493d82c5c21a12d7ba43eccc30cb;p=thirdparty%2Fkernel%2Flinux.git USB: appledisplay: close race between probe and completion handler There is a small window during probing when IO is running but the backlight is not registered. Processing events during that time will crash. The completion handler needs to check for a backlight before scheduling work. The bug is as old as the driver. Signed-off-by: Oliver Neukum CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240912123317.1026049-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c index c8098e9b432e1..62b5a30edc426 100644 --- a/drivers/usb/misc/appledisplay.c +++ b/drivers/usb/misc/appledisplay.c @@ -107,7 +107,12 @@ static void appledisplay_complete(struct urb *urb) case ACD_BTN_BRIGHT_UP: case ACD_BTN_BRIGHT_DOWN: pdata->button_pressed = 1; - schedule_delayed_work(&pdata->work, 0); + /* + * there is a window during which no device + * is registered + */ + if (pdata->bd ) + schedule_delayed_work(&pdata->work, 0); break; case ACD_BTN_NONE: default: @@ -202,6 +207,7 @@ static int appledisplay_probe(struct usb_interface *iface, const struct usb_device_id *id) { struct backlight_properties props; + struct backlight_device *backlight; struct appledisplay *pdata; struct usb_device *udev = interface_to_usbdev(iface); struct usb_endpoint_descriptor *endpoint; @@ -272,13 +278,14 @@ static int appledisplay_probe(struct usb_interface *iface, memset(&props, 0, sizeof(struct backlight_properties)); props.type = BACKLIGHT_RAW; props.max_brightness = 0xff; - pdata->bd = backlight_device_register(bl_name, NULL, pdata, + backlight = backlight_device_register(bl_name, NULL, pdata, &appledisplay_bl_data, &props); - if (IS_ERR(pdata->bd)) { + if (IS_ERR(backlight)) { dev_err(&iface->dev, "Backlight registration failed\n"); - retval = PTR_ERR(pdata->bd); + retval = PTR_ERR(backlight); goto error; } + pdata->bd = backlight; /* Try to get brightness */ brightness = appledisplay_bl_get_brightness(pdata->bd);