Jeongjun Park <aha310510@xxxxxxxxx> wrote:
>
> iowarrior_read() uses the iowarrior dev structure, but does not use any
> lock on the structure. This can cause various bugs including data-races,
> so it is more appropriate to use a mutex lock to safely protect the
> 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
> structure obtained by reading file->private_data. Therefore, it is
> better to remove the check.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 946b960d13c1 ("USB: add driver for iowarrior devices.")
> Signed-off-by: Jeongjun Park <aha310510@xxxxxxxxx>
I think this patch should be moved to the usb-linus tree to be applied in the
next rc version. iowarrior_read() is very vulnerable to a data-race because it
reads a struct iowarrior without a mutex_lock. I think this almost certainly
leads to a data-race, so I think this function should be moved to the
usb-linus tree to be fixed as soon as possible.
I would appreciate it if you could review this.
Regards,
Jeongjun Park
> ---
> v1 -> v2: Added cc tag and change log
>
> 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;
>
> dev = file->private_data;
>
> + if (file->f_flags & O_NONBLOCK) {
> + retval = mutex_trylock(&dev->mutex);
> + if (!retval)
> + return -EAGAIN;
> + } else {
> + retval = 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 = -ENODEV;
> + goto exit;
> + }
>
> dev_dbg(&dev->interface->dev, "minor %d, count = %zd\n",
> dev->minor, count);
>
> /* read count must be packet size (+ time stamp) */
> if ((count != dev->report_size)
> - && (count != (dev->report_size + 1)))
> - return -EINVAL;
> + && (count != (dev->report_size + 1))) {
> + retval = -EINVAL;
> + goto exit;
> + }
>
> /* repeat until no buffer overrun in callback handler occur */
> do {
> atomic_set(&dev->overflow_flag, 0);
> if ((read_idx = read_index(dev)) == -1) {
> /* queue empty */
> - if (file->f_flags & O_NONBLOCK)
> - return -EAGAIN;
> + if (file->f_flags & O_NONBLOCK) {
> + retval = -EAGAIN;
> + goto exit;
> + }
> else {
> //next line will return when there is either new data, or the device is unplugged
> int r = 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 = -ERESTART;
> + goto exit;
> }
> if (!dev->present) {
> //The device was unplugged
> - return -ENODEV;
> + retval = -ENODEV;
> + goto exit;
> }
> if (read_idx == -1) {
> // Can this happen ???
> - return 0;
> + retval = 0;
> + goto exit;
> }
> }
> }
>
> offset = read_idx * (dev->report_size + 1);
> if (copy_to_user(buffer, dev->read_queue + offset, count)) {
> - return -EFAULT;
> + retval = -EFAULT;
> + goto exit;
> }
> } while (atomic_read(&dev->overflow_flag));
>
> read_idx = ++read_idx == 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;
> }
>
> /*
> --
