From: Oliver Neukum <oneukum@xxxxxxx>
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@xxxxxxx>
---
drivers/usb/misc/appledisplay.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c
index ba6a5d6..55acd44 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);
--
1.8.4.5
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