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This can cause various bugs including data-races, so it is more appropriate to use a mutex lock to safely protect the=20 iowarrior dev structure. When using a mutex lock, you should split the branch to prevent blocking when the O_NONBLOCK flag is set. In addition, it is unnecessary to check for NULL on the iowarrior dev=20 structure obtained by reading file->private_data. Therefore, it is=20 better to remove the check. Fixes: 946b960d13c1 ("USB: add driver for iowarrior devices.") Signed-off-by: Jeongjun Park --- drivers/usb/misc/iowarrior.c | 46 ++++++++++++++++++++++++++++-------- 1 file changed, 36 insertions(+), 10 deletions(-) diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c index 6d28467ce352..a513766b4985 100644 --- a/drivers/usb/misc/iowarrior.c +++ b/drivers/usb/misc/iowarrior.c @@ -277,28 +277,45 @@ static ssize_t iowarrior_read(struct file *file, char= __user *buffer, struct iowarrior *dev; int read_idx; int offset; + int retval; =20 dev =3D file->private_data; =20 + if (file->f_flags & O_NONBLOCK) { + retval =3D mutex_trylock(&dev->mutex); + if (!retval) + return -EAGAIN; + } else { + retval =3D mutex_lock_interruptible(&dev->mutex); + if (retval) + return -ERESTARTSYS; + } + /* verify that the device wasn't unplugged */ - if (!dev || !dev->present) - return -ENODEV; + if (!dev->present) { + retval =3D -ENODEV; + goto exit; + } =20 dev_dbg(&dev->interface->dev, "minor %d, count =3D %zd\n", dev->minor, count); =20 /* read count must be packet size (+ time stamp) */ if ((count !=3D dev->report_size) - && (count !=3D (dev->report_size + 1))) - return -EINVAL; + && (count !=3D (dev->report_size + 1))) { + retval =3D -EINVAL; + goto exit; + } =20 /* repeat until no buffer overrun in callback handler occur */ do { atomic_set(&dev->overflow_flag, 0); if ((read_idx =3D read_index(dev)) =3D=3D -1) { /* queue empty */ - if (file->f_flags & O_NONBLOCK) - return -EAGAIN; + if (file->f_flags & O_NONBLOCK) { + retval =3D -EAGAIN; + goto exit; + } else { //next line will return when there is either new data, or the device i= s unplugged int r =3D wait_event_interruptible(dev->read_wait, @@ -309,28 +326,37 @@ static ssize_t iowarrior_read(struct file *file, char= __user *buffer, -1)); if (r) { //we were interrupted by a signal - return -ERESTART; + retval =3D -ERESTART; + goto exit; } if (!dev->present) { //The device was unplugged - return -ENODEV; + retval =3D -ENODEV; + goto exit; } if (read_idx =3D=3D -1) { // Can this happen ??? - return 0; + retval =3D 0; + goto exit; } } } =20 offset =3D read_idx * (dev->report_size + 1); if (copy_to_user(buffer, dev->read_queue + offset, count)) { - return -EFAULT; + retval =3D -EFAULT; + goto exit; } } while (atomic_read(&dev->overflow_flag)); =20 read_idx =3D ++read_idx =3D=3D MAX_INTERRUPT_BUFFER ? 0 : read_idx; atomic_set(&dev->read_idx, read_idx); + mutex_unlock(&dev->mutex); return count; + +exit: + mutex_unlock(&dev->mutex); + return retval; } =20 /* --