fuse: check size of FUSE_NOTIFY_INVAL_ENTRY message

FUSE_NOTIFY_INVAL_ENTRY didn't check the length of the write so the
message processing could overrun and result in a "kernel BUG at
fs/fuse/dev.c:629!"

Reported-by: Han-Wen Nienhuys <hanwenn@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@kernel.org
void fuse_abort_conn(struct fuse_conn *fc)
{
	spin_lock(&fc->lock);
	if (fc->connected) {
		fc->connected = 0;
		fc->blocked = 0;
		end_io_requests(fc);
		end_queued_requests(fc);
		end_polls(fc);
		wake_up_all(&fc->waitq);
		wake_up_all(&fc->blocked_waitq);
		kill_fasync(&fc->fasync, SIGIO, POLL_IN);
	}
	spin_unlock(&fc->lock);
}

void fuse_abort_conn(struct fuse_conn *fc)
{
	spin_lock(&fc->lock);
	if (fc->connected) {
		fc->connected = 0;
		fc->blocked = 0;
		end_io_requests(fc);
		end_queued_requests(fc);
		end_polls(fc);
		wake_up_all(&fc->waitq);
		wake_up_all(&fc->blocked_waitq);
		kill_fasync(&fc->fasync, SIGIO, POLL_IN);
	}
	spin_unlock(&fc->lock);
}
