V4L/DVB (9647): em28xx: void having two concurrent control URB's

Now that we have a polling task for IR, there's a race condition, since
IR can be polling while other operations are being doing. Also, we are
now sharing the same urb_buf for both read and write control urb
operations. So, we need a mutex.

Thanks to Davin Heitmueller <devin.heitmueller@gmail.com> for warning me.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 12 insertions, 2 deletions

diff --git a/drivers/media/video/em28xx/em28xx-core.c b/drivers/media/video/em28xx/em28xx-core.c
index 9551b8ab8c44..15e2b525310d 100644
--- a/drivers/media/video/em28xx/em28xx-core.c
+++ b/drivers/media/video/em28xx/em28xx-core.c
@@ -76,18 +76,22 @@ int em28xx_read_reg_req_len(struct em28xx *dev, u8 req, u16 reg,
 
         em28xx_regdbg("req=%02x, reg=%02x ", req, reg);
 
+        mutex_lock(&dev->ctrl_urb_lock);
         ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), req,
                               USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                               0x0000, reg, dev->urb_buf, len, HZ);
         if (ret < 0) {
                 if (reg_debug)
                         printk(" failed!\n");
+                mutex_unlock(&dev->ctrl_urb_lock);
                 return ret;
         }
 
         if (len)
                 memcpy(buf, dev->urb_buf, len);
 
+        mutex_unlock(&dev->ctrl_urb_lock);
+
         if (reg_debug) {
                 printk("%02x values: ", ret);
                 for (byte = 0; byte < len; byte++)
@@ -112,16 +116,18 @@ int em28xx_read_reg_req(struct em28xx *dev, u8 req, u16 reg)
 
         em28xx_regdbg("req=%02x, reg=%02x:", req, reg);
 
+        mutex_lock(&dev->ctrl_urb_lock);
         ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), req,
                               USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                               0x0000, reg, dev->urb_buf, 1, HZ);
+        val = dev->urb_buf[0];
+        mutex_unlock(&dev->ctrl_urb_lock);
+
         if (ret < 0) {
                 printk(" failed!\n");
                 return ret;
         }
 
-        val = dev->urb_buf[0];
-
         if (reg_debug)
                 printk("%02x\n", (unsigned char) val);
 
@@ -156,10 +162,12 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
                 printk("\n");
         }
 
+        mutex_lock(&dev->ctrl_urb_lock);
         memcpy(dev->urb_buf, buf, len);
         ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0), req,
                               USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                               0x0000, reg, dev->urb_buf, len, HZ);
+        mutex_unlock(&dev->ctrl_urb_lock);
 
         if (dev->wait_after_write)
                 msleep(dev->wait_after_write);
diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index bca5955339b8..c32fc7d24a42 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -1936,6 +1936,7 @@ static int em28xx_init_dev(struct em28xx **devhandle, struct usb_device *udev,
 
         dev->udev = udev;
         mutex_init(&dev->lock);
+        mutex_init(&dev->ctrl_urb_lock);
         spin_lock_init(&dev->slock);
         init_waitqueue_head(&dev->open);
         init_waitqueue_head(&dev->wait_frame);
diff --git a/drivers/media/video/em28xx/em28xx.h b/drivers/media/video/em28xx/em28xx.h
index 1adf3d9d9bff..5956e9b3062f 100644
--- a/drivers/media/video/em28xx/em28xx.h
+++ b/drivers/media/video/em28xx/em28xx.h
@@ -433,6 +433,7 @@ struct em28xx {
 
         /* locks */
         struct mutex lock;
+        struct mutex ctrl_urb_lock;     /* protects urb_buf */
         /* spinlock_t queue_lock; */
         struct list_head inqueue, outqueue;
         wait_queue_head_t open, wait_frame, wait_stream;