Re: [lvc-project] [PATCH] [RFC] net: smc: fix fasync leak in smc_release()

On Thu, 2024-03-07 at 13:21 +0300, Dmitry Antipov wrote:

On Thu, 2024-03-07 at 10:57 +0100, Jan Karcher wrote:

quoted

We think it might be an option to secure the path in this function with 
the smc->clcsock_release_lock.

	lock_sock(&smc->sk);
	if (smc->use_fallback) {
		if (!smc->clcsock) {
			release_sock(&smc->sk);
			return -EBADF;
		}
+		mutex_lock(&smc->clcsock_release_lock);
		answ = smc->clcsock->ops->ioctl(smc->clcsock, cmd, arg);
+		mutex_unlock(&smc->clcsock_release_lock);
		release_sock(&smc->sk);
		return answ;
	}

What do yo think about this?

You're trying to fix it on the wrong path. FIOASYNC is a generic rather
than protocol-specific thing. So userspace 'ioctl(sock, FIOASYNC, [])'
call is handled with:

-> sys_ioctl()
  -> do_vfs_ioctl()
    -> ioctl_fioasync()
      -> filp->f_op->fasync() (which is sock_fasync() for all sockets)

rather than 'sock->ops->ioctl(...)'.

Any progress on this?

Dmitry