diff options
| author | Oliver Neukum <oneukum@suse.de> | 2014-05-19 13:53:55 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-05-27 16:03:57 -0700 |
| commit | 552e1f2679b7b766b8b8de3dc6d83d9cd28f28b2 (patch) | |
| tree | 1e696b32dccada97e0aa1431daf1f8c8a23a0d75 | |
| parent | d846b7650db3fcca7901b6e23f6416c3601a3dfe (diff) | |
USB: appledisplay: fix race between reading and writing from the device
The workqueue handler may call appledisplay_bl_get_brightness() while
user space calls appledisplay_bl_update_status(). As they share a
buffer that must not happen. Use a mutex for mutual exclusion.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/misc/appledisplay.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c index f37c78d1bdf4..b3d245ef46ef 100644 --- a/drivers/usb/misc/appledisplay.c +++ b/drivers/usb/misc/appledisplay.c @@ -81,6 +81,7 @@ struct appledisplay { struct delayed_work work; int button_pressed; spinlock_t lock; + struct mutex sysfslock; /* concurrent read and write */ }; static atomic_t count_displays = ATOMIC_INIT(0); @@ -144,6 +145,7 @@ static int appledisplay_bl_update_status(struct backlight_device *bd) struct appledisplay *pdata = bl_get_data(bd); int retval; + mutex_lock(&pdata->sysfslock); pdata->msgdata[0] = 0x10; pdata->msgdata[1] = bd->props.brightness; @@ -156,15 +158,17 @@ static int appledisplay_bl_update_status(struct backlight_device *bd) 0, pdata->msgdata, 2, ACD_USB_TIMEOUT); - + mutex_unlock(&pdata->sysfslock); + return retval; } static int appledisplay_bl_get_brightness(struct backlight_device *bd) { struct appledisplay *pdata = bl_get_data(bd); - int retval; + int retval, brightness; + mutex_lock(&pdata->sysfslock); retval = usb_control_msg( pdata->udev, usb_rcvctrlpipe(pdata->udev, 0), @@ -174,11 +178,13 @@ static int appledisplay_bl_get_brightness(struct backlight_device *bd) 0, pdata->msgdata, 2, ACD_USB_TIMEOUT); + brightness = pdata->msgdata[1]; + mutex_unlock(&pdata->sysfslock); if (retval < 0) return retval; else - return pdata->msgdata[1]; + return brightness; } static const struct backlight_ops appledisplay_bl_data = { @@ -241,6 +247,7 @@ static int appledisplay_probe(struct usb_interface *iface, spin_lock_init(&pdata->lock); INIT_DELAYED_WORK(&pdata->work, appledisplay_work); + mutex_init(&pdata->sysfslock); /* Allocate buffer for control messages */ pdata->msgdata = kmalloc(ACD_MSG_BUFFER_LEN, GFP_KERNEL); |