snprintf() always returns the full length of the string it could have printed, even if it was truncated because the buffer was too small. So in case the counter value is truncated, we will over-read from in_buffer and over-write to the caller's buffer. I don't think it's actually possible for this to happen, but in case truncation occurs, WARN and return -EIO. Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx> --- drivers/usb/misc/yurex.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c index 1232dd49556d..6d9fd5f64903 100644 --- a/drivers/usb/misc/yurex.c +++ b/drivers/usb/misc/yurex.c @@ -413,6 +413,9 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count, spin_unlock_irqrestore(&dev->lock, flags); mutex_unlock(&dev->io_mutex); + if (WARN_ON_ONCE(len >= sizeof(in_buffer))) + return -EIO; + return simple_read_from_buffer(buffer, count, ppos, in_buffer, len); } -- Ben Hutchings, Software Developer Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom
